A bio-inspired coordination polymer as outstanding water oxidation catalyst via second coordination sphere engineering

Ferric citrate corroding nickel foam to synthesize carbon quantum dots@nickel-iron layered double hydroxide microspheres for efficient water oxidation

The design of oxygen evolution reaction (OER) catalysts with high catalytic efficiency and durability is of great significance for promoting hydrogen production via water electrolysis. Here, a one-step hydrothermal method was used to synthesize carbon quantum dots@nickel-iron layered double hydroxide (CQDs@NiFe-LDH) composites based on corrosion engineering. The introduction of carbon quantum dots (CQDs) effectively modulates the electronic structure and charge distribution of nickel-iron layered double hydroxide (NiFe-LDH), resulting in high oxygen evolution reaction with an overpotential of 257 mV at 100 mA cm-2 and a small Tafel slope of 38.73 mV dec-1. Furthermore, CQDs@NiFe-LDH can be operated continuously for 300 and 100 h without the significant performance degradation at a current density of 100 mA cm-2 in 1 M KOH and seawater solutions, respectively, indicating high catalytic stability. The excellent OER capabilities of CQDs@NiFe-LDH is attributed to the fact that CQDs can not only modulate the electronic structure of NiFe-LDH but also facilitate the transfer of protons between intermediates during the oxygen evolution reaction (OER), thereby enhancing the material's intrinsic catalytic activity.

Bio-inspired nickel-iron-based organogel: an efficient and stable bifunctional electrocatalyst for overall water splitting at high current density

Developing a platinum group metal (PGM) free electrocatalyst remains a prime challenge for cost effective green hydrogen (H2) production. Herein, mimicking the PS II catalyst, a bimetallic organogel of nickel (Ni2+), iron (Fe3+) and benzotriazole (NiFe-gel) is developed as an efficient electrocatalyst. The developed synthetic strategy is simple and scalable, and most importantly, no binder is required for gel-loaded electrode preparation. The respective gel-based electrode showed excellent bifunctionality, in both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), water electrolysis activity in low and high current density (η10: 110 mV and η1000: 260 mV for the OER and η10: 88 mV and η1000: 324 mV for the HER), low Tafel slope and outstanding stability for 100 h at a current density of 1 A cm-2. The two-electrode electrolyser using the developed NiFe-gel in the anode and cathode setups for overall water splitting attained current densities of 10 mA cm-2 and 1 A cm-2 at potentials of 1.49 V and 1.89 V, respectively. Most significantly, NiFe-gel loaded anion exchange membrane based 4 cm2 alkaline water electrolysis (AEMAWE) attained a current density of 1.08 A cm-2 at 50 °C and 2 V and showed stability for at least 100 h. Very nominal performance reduction was observed upon scale-up of the electrolyser from 4 cm2 to 9 cm2, and the performance was better than the targeted AEMAWE performance of ≥1 A cm-2 at 2 V. This excellent performance is attributed to the synergistic electronic interaction between Fe3+ and Ni2+, interaction of nitrogen rich triazole moieties attached to the metal site, similar to the PS II system, and porous electrode microstructure. Thus, the NiFe-gel might be a potential PGM-free electrocatalyst for industrial scale hydrogen production through water electrolysis.

Cooperative promotion of electroreduction of CO to n-propanol by *CO enrichment and proton regulation

The CO2/CO electroreduction reaction (CO2RR/CORR) to liquid products presents an enticing pathway to store intermittent renewable electricity. However, the selectivity for desirable high-value C3 products, such as n-propanol, remains unsatisfactory in the CO2RR/CORR. Here, we report that *CO enrichment and proton regulation cooperatively enhance C1-C2 coupling by increasing CO pressure and utilizing proton sponge modification, promoting the production of n-propanol over a Cu0/Cu+ nanosheet catalyst in the CORR. We obtain an impressive faradaic efficiency (FE) of 44.0% ± 2.3% for n-propanol at a low potential of -0.44 V vs. reversible hydrogen electrode (RHE) under 3 bar CO. Experimental results demonstrated that *H intermediates could be regulated by proton sponge modification. In situ characterization combined with density functional theory (DFT) calculations validate that Cu+ species exist stably in proton sponge-modified Cu-based catalysts along with appropriate *CO coverage. This design facilitates the potential-determining C1-C1 and C1-C2 coupling steps and contributes to the n-propanol production.

Real-Time Monitoring of Fe-Induced Stable γ-NiOOH in Binder-Free FeNi MOF Electrocatalysts for Enhanced Oxygen Evolution

Hydrogen energy is a promising renewable source, and metal-organic frameworks (MOFs) are considered potential electrocatalysts for water electrolysis due to their abundant active sites, high porosity, and large surface area. The synthesis of bimetallic iron-nickel-benzene-1,3,5-tricarboxylate/nickel foam (FeNi-BTC/NF) MOF is reported using a binder-free one-pot method by immersing nickel foam (NF) into a solution of benzene-1,3,5-tricarboxylic acid (BTC), N,N-dimethylformamide (DMF), and iron (Fe) salts. FeNi-BTC/NF exhibits a low overpotential of 276 mV at 100 mA cm- 2, a Tafel slope of 94 mV dec-1, and stability exceeding 120 h. The Fe-Ni interaction facilitates the formation of a stable gamma-nickel oxyhydroxide (γ-NiOOH) phase, preventing its reversion to nickel hydroxyide (Ni(OH)₂), which is crucial for improving oxygen evolution reaction (OER) performance. This phase transition, revealed via in situ Raman spectroelectrochemical analysis, enhances electrocatalytic activity. Additionally, high-valent Fe modulates the electronic structure of Ni, enabling FeNi-BTC/NF to transform into γ-NiOOH at higher potentials, with Fe and γ-NiOOH synergistically boosting OER efficiency. The findings offer insights into Fe/Ni atom interactions and phase transformations in FeNi-BTC/NF MOFs for enhanced water splitting.

Histidine-Based "Transfer Stations" at Carbon-Immobilized Metal Particles Enable Rapid Hydrogen Transfer for Efficient Formic Acid Dehydrogenation

The interaction of surface metal species with the solution plays a key role in engineering heterogeneous catalytic processes. Herein, we present the facile synthesis of L-histidine-coordinated PdAg nanoparticles (4.03 ± 0.08 nm) anchored on pristine carbon supports (denoted as PdAg-NH2/C) and their use for formic acid dehydrogenation (FAD). Significant acceleration of FAD related to the histidine is observed, and the enhancement mechanism is experimentally and theoretically investigated. The presence of L-histidine at metal sites promotes rapid binding of formic acid molecules due to acid-base interactions. The local enrichment of both protons and formate at the metal-solution interfaces promotes the subsequent formate decomposition and hydride transfer to the metal surface. The as-generated surface H species are more concentrated compared to the previously reported catalyst where the metal is loaded on an amino modified support, this enabling a significantly enhanced H2 production. The optimal Pd1Ag1-NH2/C catalyst exhibits a high turnover frequency (TOF) of 6493.5 h-1 at 333 K based on the total amount of Pd, together with an H2 selectivity of 100%. This study emphasizes the critical role of optimizing local transport pathways near catalytic centers chemically and further provides insights into the rational development of heterogeneous catalysts for FAD technologies.

Ligand-rich oxygen evolution electrocatalysts reconstructed from metal-organic frameworks for anion-exchange membrane water electrolysis

Organic ligands in metal-organic frameworks (MOFs) play an indispensable role in the reconstruction and catalysis during the alkaline oxygen evolution reaction (OER). However, it is still a big challenge to maintain a high content of ligands in MOF-reconstructed OER electrocatalysts and to study the interaction between ligands and derived (oxy)hydroxides. Herein, a ligand-rich trimetallic amorphous electrocatalyst is fabricated through a two-step mechanochemical and electrochemical reconstruction strategy. Experimental and theoretical studies clearly reveal that the d-π interaction between delocalized π-electrons on the benzene ring of ligands and derived (oxy)hydroxides, can trigger the charge transfer from ligands to the active metal centers, thus optimizing the adsorption energy of the oxygen-containing intermediates and enhancing the OER performance. Moreover, an anion-exchange membrane water electrolyzer using such ligand-rich OER electrocatalyst can be operated steadily at 1.69 V and 55 °C under an industrial-level current density of 500 mA cm-2 for over 200 h. This work provides novel insights into the role of organic ligands in alkaline OER electrocatalysis, with the potential to facilitate the production of green hydrogen at industrial-level current densities.

Cooperative Cobalt-Doped and Carboxylate Anions Modification of NiFe-Layered Double Hydroxides for Improving Oxygen Evolution Reaction

The disparity of the fast electron-slow proton process significantly hinders the catalytic efficiency of the oxygen evolution reaction (OER) in water splitting, so it is necessary to develop efficient and stable catalytic materials to mitigate elevated overpotentials. In this study, a one-step hydrothermal approach was utilized to synthesize a cobalt-doped, carboxylic-acid-modified NiFe-layered double hydroxide (CoNiFe-LDH/NF) catalyst with significantly enhanced intrinsic catalytic activity. Introducing Co promotes the generation of active components, and carboxylate anions accelerate proton transfer, the synergistic interaction of which endows CoNiFe-LDH/NF with superior OER performance. Experimental results show that the catalyst has an overpotential as low as 230 mV at 100 mA cm-2, a Tafel slope as low as 38.5 mV dec-1, and excellent stability for 120 h at a current density of 10 mA cm-2. Furthermore, mechanistic exploration by molecular probe detection and the pH-dependent experiment showed that the modified CoNiFe-LDH/NF was closer to the lattice oxygen oxidation mechanism (LOM). This study provides an effective strategy to improve the performance of layered OER catalytic materials.

Enhancing catalytic durability in alkaline oxygen evolution reaction through squaric acid anion intercalation

The corrosive acidic interfacial microenvironment caused by rapid multi-step deprotonation of alkaline oxygen evolution reaction in industrial high current water electrolysis is one of the key problems limiting its stability. Some functional anions derived from electrocatalysis exhibit special functionalities in modulating the interface microenvironment, but this matter has not received adequate attention in academic discussions. Here we show that the coordinate squaric acid undergoes a dissolve-re-intercalation process in alkaline oxygen evolution, leading to its stabilization within the Fe-doped NiOOH interlayer in the form of the squaric acid anions (NiFe-SQ/NF-R). These intercalated squaric acid anions stabilizes OH- through multiple hydrogen bond interactions, which is conducive to maintaining high catalytic interface alkalinity. Hence, the interfacial acidification of prepared NiFe-SQ/NF-R is inhibited, resulting in a tenfold prolong in its catalytic durability (from 65 to 700 h) when exposed to 3.0 A cm-2, as opposed to NiFe-LDH/NF-R. This derived functional anion guarantees the enduring performance of the NiFe-derived electrocatalyst under high current densities by controlling the interfacial alkalinity.

Entropy-Driven Competitive Adsorption Sites Tailoring Unlocks Efficient Hybrid Conversion Zn-Air Batteries

Hybrid conversion Zn-air batteries (HC-ZABs) epitomize a typical integrated energy storage and conversion device that advances green chemistry and reduces carbon emissions. However, balancing efficiency and selectivity of electrocatalytic cathodic reactions remains the bottleneck in such batteries. Herein, we address this issue by designing a high-entropy perovskite, La0.6Sr0.1Ca0.1Rb0.1Y0.1CoO3 (HE-LCO), which outperforms conventional perovskites in offering enhanced electrocatalytic activity, better selectivity, and outstanding stability for cathodic benzyl alcohol oxidation reaction (BAOR). Combined spectroscopy characterizations, operando measurements, and theoretic calculations reveal that the entropy-driven modulation of the second coordination sphere in HE-LCO balances the adsorption of nucleophile benzyl alcohol and OH-, while inhibiting competing oxygen evolution reaction (OER). Based on this rationalized HE-LCO electrocatalyst, HC-ZABs realized efficient energy storage and benzoic acid production, boasting a long lifespan of 900 cycles at 20 mA cm-2 and 6.7 mAh cm-2 per cycle. Further, practical ampere-hour-scale HC-ZABs demonstrated a 62.8% energy efficiency improvement and an average benzoic acid yield of 0.85 g per cycle, highlighting the potential of this integrated device for simultaneous sustainable energy storage and green electrochemical synthesis.

2D Metastable-Phase Hafnium Oxide Triggers Hydrogen Spillover for Boosting Hydrogen Production

Hydrogen (H) manipulation plays a significantly important role in many important applications, in which the occurrence of hydrogen spillover generally shows substrate-dependent behavior. It therefore remains an open question about how to trigger the hydrogen spillover on the substrates that are generally hydrogen spillover forbidden. Here a new metastable-phase 2D edge-sharing oxide: six-hexagonal phase-hafnium oxide (Hex-HfO2, space group: P63mc (186)) with the coordination number of six is demonstrated, which serves as an ideal platform for activating efficient hydrogen spillover after loading Ru nanoclusters (Ru/Hex-HfO2). For a stark comparison, the hydrogen spillover is strongly forbidden when using stable monoclinic phase HfO2 (M-HfO2, space group: P21/c (14), coordination number: seven) as the substrate. When applied in an acidic hydrogen evolution reaction (HER), Ru/Hex-HfO2 exhibits a low overpotential of 8 mV at 10 mA cm-2 and a high Ru utilization activity of 14.37 A mgRu -1 at 30 mV. Detailed mechanism reveals the positive H adsorption free energy on Hex-HfO2, indicating that H is more likely to spillover on Hex-HfO2. Furthermore, the strong interaction between Ru and Hex-HfO2 optimizes the desorption of hydrogen intermediate, thus facilitating the surface H spillover. The discovery provides new guidance for developing metastable-phase oxide substrates for advanced catalysis.

Metal Exchange in Thioguanosine Coordination Polymers of Gold (I) and Silver (I)

Heterometallic coordination polymers of Au(I) and Ag(I) with 6-thioguanosine, poly([ Au x Ag 1 - x ( 6 - tG ) ] ${[{\rm{Au}}_{\rm{x}} {\rm{Ag}}_{1 - x} {\rm{(6}} - {\rm{tG)}}]}$ ), have been prepared and were observed to form hydrogels. We find that the composition of the heterometallic polymer is proportional to the mole fractions of the metals in the preparation solution. Optical absorption spectra show single peaks forλ > 300 ${\lambda \char62 300}$ nm which can be interpolated in a linear manner between x= 0 . 0 ${ = 0.0}$ and x= 1 . 0 ${ = 1.0}$ consistent with the formation of a heterometallic polymer rather than a mixture of homopolymers. However photoluminescence and circular dichroism spectra are sensitive to the supramolecular structure of the polymers and show more complex behaviour. Atomic force microscopy indicated that the molecular chains of the Au homopolymer entwine to form strands that are predominantly right-hand helices. The Ag homopolymer has previously been shown to form left-hand helices. Intermediate compositions have more complex structures because of the competition between the left and right-handed preferences of the homopolymers. Finally, we have shown that the metal-ligand bonds are labile on a timescale of about 5 h at ambient temperature (about 293 K). Mixtures of homopolymers transform to the corresponding heterometallic coordination polymer by metal exchange as judged by optical absorption, photoluminescence and circular dichroism spectra.

Degradation of Organic Matter in Sauce-Flavored Liquor Wastewater by Catalytic Oxidation Performance of Mn2Cu2Ox/Al2O3 Catalysts in Treatment and Mechanism Research

With the rapid growth of the sauce-flavored liquor industry, the treatment of wastewater has become an increasingly critical challenge. This study seeks to assess the catalytic oxidation efficacy of Mn2Cu2Ox/Al2O3 catalysts in the degradation of organic pollutants present in sauce-flavored liquor wastewater, while also elucidating the mechanisms underpinning their performance. Mn2Cu2Ox/Al2O3 catalysts were synthesized, and their physicochemical properties were thoroughly characterized using advanced techniques such as Brunauer-Emmett-Teller (BET) analysis, N2 sorption isotherm analysis, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Moreover, the key active species involved in the catalytic oxidation process, including hydroxyl radicals (•OH) and superoxide anion radicals (•O2-), were identified through hydroxyl radical quenching experiments employing tertiary butyl alcohol (TBA). The contribution of these free radicals to enhancing the ozone catalytic oxidation performance was also systematically evaluated. Based on both experimental data and theoretical analyses, the Mn2Cu2Ox/Al2O3 catalysts demonstrate remarkable catalytic activity and stability, significantly reducing chemical oxygen demand (COD) levels in wastewater. Furthermore, the catalysts are capable of activating oxygen molecules (O2) during the reaction, producing reactive oxygen species, such as •O2- and •OH, which are potent oxidizing agents that effectively decompose organic pollutants in wastewater. The proposed catalysts represent a highly promising solution for the treatment of sauce-flavored liquor wastewater and lays a solid foundation for its future industrial application.

Water oxidation on a sustainable polymeric proton relay: the role of post-phosphating of an oxide sub-layer on PCET

Lagging proton transfer (PT) toward electron transfer (ET) during multi-step proton-coupled electron transfer (PCET) is one of the humble approaches toward complete biomimicking of artificial leaves. In this work, we synthesized a typical sustainable polymeric interface (poly L-lysine) to investigate the effect of post-phosphating of the metal oxide substrate (NF/CoMoO4) on the yield of PCET during the electrocatalytic water oxidation reaction (WOR) in alkaline medium. The details of the PCET mechanism are unraveled using the kinetic isotope effect (KIE), proton inventory, Tafel slopes, pH studies, and high-frequency transmission line (Gerischer) impedance. The appealing Gerischer feature unveils an electrochemical reaction preceded and followed by a chemical exchange reaction (CEC mechanism), indicating a proton hopping mechanism that practically blocks natural diffusion of the protonic species (H+ and H2O) and the role of the interfacial phosphate#p-Lys hydrogen bond network (HBN) in PCET. The interfacial HBN can serve as a flexible proton hook to delocalize protons and may polarize the O-O bond, thereby facilitating the overall PCET for the progress of O-O bond formation. Poly L-lysine improved the response stability of the PCET catalyst through corrosion protection of the metallic substrate and also prevention of the spatiotemporal accumulation of protons as a surface corrosion agent. The results show a non-concerted PCET mechanism with the first ET step as the RDS of the heterogeneous WOR.

NiCu-layered double hydroxide-modified CuO nanorods for enhanced non-enzymatic glucose sensing

A flexible non-enzymatic glucose sensor with high sensitivity (NiCu-LDH/CuO/NCC) was prepared by growing NiCu-layered double hydroxide (NiCu-LDH)-modified CuO nanorods on N-doped carbon cloth (NCC) using hydrothermal method and electrodeposition. The NCC provided abundant attachment sites and good electrical conductivity for CuO nanorods, and the hierarchical nanostructures (NiCu-LDH/CuO) had large specific surface area and highly catalytic active sites, which facilitated the electrooxidation of glucose. The effect of the ratio of Ni to Cu on the electrocatalytic performance of NiCu-LDH/CuO/NCC was evaluated. The results indicated that the optimized NiCu-LDH/CuO/NCC (Ni/Cu molar ratio of 2:1) had good electrocatalytic oxidation toward glucose, and exhibited high sensitivity (11.545 mA cm-2 mM-1), low detection limit (0.26 μM), large linear range (0.001-1.5 mM), and good stability (95% after 28 days). Therefore, the hierarchical nanostructure is suitable for the construction of flexible non-enzymatic glucose sensors with high sensitivity, indicating that the combination of transition metal oxides and LDH provides a unique opportunity for designing high-performance electrochemical non-enzymatic glucose sensors.

Spillover of active oxygen intermediates of binary RuO2/Nb2O5 nanowires for highly active and robust acidic oxygen evolution

Over-oxidation of surface ruthenium active sites of RuOx-based electrocatalysts leads to the formation of soluble high-valent Ru species and subsequent structural collapse of electrocatalysts, which results in their low stability for the acidic oxygen evolution reaction (OER). Herein, a binary RuO2/Nb2O5 electrocatalyst with abundant and intimate interfaces has been rationally designed and synthesized to enhance its OER activity in acidic electrolyte, delivering a low overpotential of 179 mV at 10 mA cm-2, a small Tafel slope of 73 mV dec-1, and a stabilized catalytic durability over a period of 750 h. Extensive experiments have demonstrated that the spillover of active oxygen intermediates from RuO2 to Nb2O5 and the subsequent participation of lattice oxygen of Nb2O5 instead of RuO2 for the acidic OER suppressed the over-oxidation of surface ruthenium species and thereby improved the catalytic stability of the binary electrocatalysts.

Preparation and characterization of graphene oxide-based cation, chelating, and anion exchangers for salt removal

Due to the shortage of freshwater resources, and the limitations of commonly used ion exchangers, this study aims to prepare, characterize, and test new graphene-based ion exchangers for salt removal. Graphene oxide (GO) was prepared using an oxidative exfoliation method. Using amide coupling, the GO surface was functionalized with taurine to produce a cation exchanger (GOT), and pentaethylenehexamine (PEHA) to produce a chelating ion exchanger (GOP) which was converted to a quaternary ammonium salt (GOQ) which acts as an anion exchanger. The surface area of GO was 220 m2/g, however, decreased tremendously on surface functionalization. X-ray diffraction (XRD) showed that the produced ion exchangers possess amorphous nature. Energy dispersive spectroscopy (EDS) showed the presence of nitrogen in GOP, GOQ, and GOT; and sulfur on GOT. X-ray photon spectroscopy (XPS) showed the presence of -SO3 and S-O on GOT, amine on GOP, and quaternary ammonium group (-NHR2 +) on GOQ. TGA shows that GO functionalization is covalent. The produced ion exchangers show an efficient removal of both the cations and anions from the individual salt solution of Ca(NO3)2, MgSO4, and NaCl. GOP sorbs both Ca2+ and Mg2+ via chelation while their anions are sorbed via ion pairing. GOT sorbs the cations via ion exchange while anions are sorbed via ion pairing. GOQ sorbs the anions via electrostatic interaction while the cations are sorbed via ion pairing. Under the experimental conditions in this study, GOP shows the best removal of Ca2+ (80.2 %) and Mg2+ (64 %) while GOT shows the best removal of Na+ (30 %). For anions, GOQ shows the best removal of NO3 - (53.5 %), SO4 2- (84 %), and Cl- (81.8 %). The GO-based ion exchangers seem promising for salt removal from water in addition to being robust at high temperatures and pH.

Breaking linear scaling relationships in oxygen evolution via dynamic structural regulation of active sites

The universal linear scaling relationships between the adsorption energies of reactive intermediates limit the performance of catalysts in multi-step catalytic reactions. Here, we show how these scaling relationships can be circumvented in electrochemical oxygen evolution reaction by dynamic structural regulation of active sites. We construct a model Ni-Fe2 molecular catalyst via in situ electrochemical activation, which is able to deliver a notable intrinsic oxygen evolution reaction activity. Theoretical calculations and electrokinetic studies reveal that the dynamic evolution of Ni-adsorbate coordination driven by intramolecular proton transfer can effectively alter the electronic structure of the adjacent Fe active centre during the catalytic cycle. This dynamic dual-site cooperation simultaneously lowers the free energy change associated with O-H bond cleavage and O-O bond formation, thereby disrupting the inherent scaling relationship in oxygen evolution reaction. The present study not only advances the development of molecular water oxidation catalysts, but also provides an unconventional paradigm for breaking the linear scaling relationships in multi-intermediates involved catalysis.

Amorphization engineering of Ni-cysteine coordination composition for urea electro-oxidation at large current density

Unavoidable oxygen evolution reaction (OER) and the relatively high potential to form real active sites of Ni3+ species severely decrease the efficiency of urea-assisted hydrogen generation facility. Herein, amorphization Ni-cysteine coordination (aNi-cys) is constructed as efficient urea electro-oxidation reaction (UOR) catalyst with highly capable of suppressing competitive OER and promoting the Ni2+ to Ni3+ in-situ electrochemical configuration through deliberately regulating the Ni/l-cysteine coordination environment. The abundant ligand atoms (N, S, and O) of l-cysteine considerably tuned the Ni electronic structure to the most suitable state while the amorphization thin lamellas increased the exposed active sites and befitting for the access of electrolyte to electrode surface, resulting improved UOR activity with a large peak current density of 263 mA cm-2, far exceeding crystalline Ni-cysteine coordination (cNi-cys) and long-term stability for 50 h working. Excitingly, only 41 kWh is required to produce 1 kg H2 (50 mA cm-2) from a home-made urea-assisted simulated seawater electrolysis apparatus, about 8 kWh energy saving from that of water splitting. This work gives a clue for preparing advanced electrocatalysts applicable to urea-related energy system with large current density.

Deciphering the Radial Ligand Effect of Biomimetic Amino Acid toward Stable Alkaline Oxygen Evolution

Mismatched electron and proton transport rates impede the manifestation of effective performance of the electrocatalytic oxygen evolution reaction (OER), thereby limiting its industrial applications. Inspired by the natural protein cluster in PS-II, different organic-inorganic hybrid electrocatalysts were synthesized via a hydrothermal method. p-Toluidine (PT), benzoic acid (BA), and p-aminobenzoic acid (PABA) were successfully intercalated into NiFe-LDH. Compared to the organic molecules containing a single functional group, the coexistence of carboxyl and amino groups served as the electron acceptor and donor, respectively, thereby optimizing the electronic structure and suppressing metal dissolution. The overpotential of the PABA-modified catalyst (NiFe-LDH-PABA) was significantly reduced to 225 mV at 10 mA cm-2, and the Tafel slope was only 38.7 mV dec-1. At a high current density of 500 mA cm-2, the NiFe-LDH-PABA catalyst can work stably in a 1 M KOH solution at 25 °C over 550 h with 96% retention of its initial activity. Density functional theory (DFT) calculations further confirmed that the work offers significant insight into the modulation by organic molecular structure and provides a new paradigm for creating organic-inorganic hybrid OER catalysts.

Improving CO2 electroconversion by customizing the hydroxyl microenvironment around a semi-open Co-N2O2 configuration

Constructing local microenvironments is one of the important strategies to improve the electrocatalytic performances, such as in electrochemical CO2 reduction (ECR). However, effectively customizing these microenvironments remains a significant challenge. Herein, utilizing carbon nanotube (CNT) heterostructured semi-open Co-N2O2 catalytic configurations (Co-salophen), we have demonstrated the role of the local microenvironment on promoting ECR through regulating the location of hydroxyl groups. Concretely, compared with the maximum Faradaic efficiency (FE) of 62% for carbon monoxide (CO) presented by Co-salophen/CNT without a hydroxyl microenvironment, the designed Co-salophen-OH3/CNT, featuring hydroxyl groups at the Co-N2O2 structural opening, shows remarkable CO2-to-CO electroreduction activity across a wide potential window, with the FE of CO up to 95%. In particular, through the deuterium kinetic isotope experiments and theoretical calculations, we decoded that the hydroxyl groups act as a proton relay station, promoting the efficient transfer of protons to the Co-N2O2 active sites. The finding demonstrates a promising molecular design strategy for enhancing electrocatalysis.

Hydrogen-Bond-Regulated Mechanochemical Synthesis of Covalent Organic Frameworks: Cocrystal Precursor Strategy for Confined Assembly

Two-dimensional imine covalent organic frameworks (2D imine-COFs) are crystalline porous materials with broad application prospects. Despite the efforts into their design and synthesis, the mechanisms of their formation are still not fully understood. Herein, a one-pot two-step mechanochemical cocrystal precursor synthetic strategy is developed for efficient construction of 2D imine-COFs. The mechanistic investigation demonstrated that the cocrystal precursors of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT) and p-toluenesulphonic acid (PTSA) sufficiently regulate the crystalline structure of COF. Evidenced by characterizations and theoretical studies, a helical hydrogen-bond network was constructed by the N-H⋅⋅⋅O supramolecular synthons between amino and sulfonic groups in TAPT-PTSA, demonstrating the role of cocrystals in promoting the organized stacking of interlayer π-π interactions, layer arrangement, and interlayer spacing, thus facilitating the orderly assembly of COFs. Moreover, the protonation degree of TAPT amines, which tuned nucleophilic directionality, enabled the sequential progression of intra- and interlayer imine condensation reactions, inhibiting the formation of amorphous polymers. The transformation from cocrystal precursors to COFs was achieved through comprehensive control of hydrogen bond and covalent bond sites. This work significantly advances the concept of hydrogen-bond-regulated COF assembly and its mechanochemical method in the design and synthesis of 2D imine-COFs, further elucidating the mechanistic aspects of their mechanochemical synthesis.

Valence Band-Tunable NiFe Electrocatalyst Triggered by the Dynamic Mo Exudation and Re-Deposition for Superior High Current Density Oxygen Evolution Reaction

Developing energy- and time-efficient strategies to derive high-performance non-precious electrocatalysts for anodic oxygen evolution reaction (OER), especially stably working at industrial-demanding current density, is still a big challenge. In this work, a concise molten salt erosion scenario was devised to rapidly modulate the smooth surface of the commercial NiMo foam substrate into the rough, electronically coupled, and hierarchically porous Ni/Fe/Mo(oxy)hydroxide catalyst layer assembled by the nanosphere array. This self-supported catalyst is super-hydrophilic for the alkaline electrolyte and distinguished by a balanced Mo leaching/surface-readsorption process to tune the metal d band center and electronic perturbation. The altered electronic environment with the favored OER intermediate adsorption behavior attains the outstanding OER activity in terms of a very small overpotential of 230.21 mV at 10 mA cm-2 and an ultra-long stability for 1179.45 h to sustain the initial commercial-level current density of ca. 1000 mA cm-2. This superb performance transcends most of the edge-cutting transition metal peers reported recently and can satisfy the standards of industrial applications. This industrial-compatible synthesis technology holds profound implications for hydrogen production via water splitting and other electrochemical applications.

A Mechanistic Insight into the Acidic-stable MnSb2O6 for Electrocatalytic Water Oxidation

The abundant, active, and acidic-stable catalysts for the oxygen evolution reaction (OER) are rare to proton exchange membrane-based water electrolysis. Mn-based materials show promise as electrocatalysts for OER in acid electrolytes. However, the relationship between the stability, activity and structure of Mn-based catalysts in acidic environments remains unclear. In this study, phase-pure MnSb2O6 was successfully prepared and investigated as a catalyst for OER in a sulfuric acid solution (pH of 2.0). A comprehensive mechanistic comparison between MnSb2O6 and Mn3O4 revealed that the rate-determining step for OER on MnSb2O6 is the direct formation of MnIV=O from MnII-H2O by the 2H+/2e- process. This process avoids the rearrangement of adjacent MnIII intermediates, leading to outstanding stability and activity.

Tracking the correlation between spintronic structure and oxygen evolution reaction mechanism of cobalt-ruthenium-based electrocatalyst

Regulating the spintronic structure of electrocatalysts can improve the oxygen evolution reaction performance efficiently. Nonetheless, the effects of tuning the spintronic structure for the oxygen evolution reaction mechanisms have rarely been discussed. Here, we show a ruthenium-cobalt-tin oxide with optimized spintronic structure due to the quantum spin interaction of Ru and Co. The specific spintronic structure of ruthenium-cobalt-tin oxide promotes the charge transfer kinetics and intermediates evolution behavior under applied potential, generating long-lived active species with higher spin density sites for the oxygen evolution reaction after the reconstruction process. Moreover, the ruthenium-cobalt-tin oxide possesses decoupled proton-electron transfer procedure during the oxygen evolution reaction process, demonstrating that the electron transfer procedure of O-O bond formation between *O intermediate and lattice oxygen in Co-O-Ru is the rate-determining step of the oxygen evolution reaction process. This work provides rational perspectives on the correlation between spintronic structure and oxygen evolution reaction mechanism.

Steering acidic oxygen reduction selectivity of single-atom catalysts through the second sphere effect

Natural enzymes feature distinctive second spheres near their active sites, leading to exquisite catalytic reactivity. However, incumbent synthetic strategies offer limited versatility in functionalizing the second spheres of heterogeneous catalysts. Here, we prepare an enzyme-mimetic single Co-N4 atom catalyst with an elaborately configured pendant amine group in the second sphere via 1,3-dipolar cycloaddition, which switches the oxygen reduction reaction selectivity from the 4e- to the 2e- pathway under acidic conditions. Proton inventory studies and theoretical calculations reveal that the introduced pendant amine acts as a proton relay and promotes the protonation of *O2 to *OOH on the Co-N4 active site, facilitating H2O2 production. The second sphere-tailored Co-N4 sites reach optima H2O2 selectivity of 97% ± 1.13%, showing a 3.46-fold enhancement to bare Co-N4 catalyst (28% ± 1.75%). This work provides an appealed approach for enzyme-like catalyst design, bridging the gap between enzymatic and heterogeneous catalysis.

Operando Stable Palladium Hydride Nanoclusters Anchored on Tungsten Carbides Mediate Reverse Hydrogen Spillover for Hydrogen Evolution

Proton exchange membrane (PEM) electrolysis holds great promise for green hydrogen production, but suffering from high loading of platinum-group metals (PGM) for large-scale deployment. Anchoring PGM-based materials on supports can not only improve the atomic utilization of active sites but also enhance the intrinsic activity. However, in practical PEM electrolysis, it is still challenging to mediate hydrogen adsorption/desorption pathways with high coverage of hydrogen intermediates over catalyst surface. Here, operando generated stable palladium (Pd) hydride nanoclusters anchored on tungsten carbide (WCx) supports were constructed for hydrogen evolution in PEM electrolysis. Under PEM operando conditions, hydrogen intercalation induces formation of Pd hydrides (PdHx) featuring weakened hydrogen binding energy (HBE), thus triggering reverse hydrogen spillover from WCx (strong HBE) supports to PdHx sites, which have been evidenced by operando characterizations, electrochemical results and theoretical studies. This PdHx-WCx material can be directly utilized as cathode electrocatalysts in PEM electrolysis with ultralow Pd loading of 0.022 mg cm-2, delivering the current density of 1 A cm-2 at the cell voltage of ~1.66 V and continuously running for 200 hours without obvious degradation. This innovative strategy via tuning the operando characteristics to mediate reverse hydrogen spillover provide new insights for designing high-performance supported PGM-based electrocatalysts.

CoFe hydroxide towards CoP2-FeP4 heterojunction for efficient and long-term stable water oxidation

Electrochemical water splitting stands out as a promising avenue for green hydrogen production, yet its efficiency is fundamentally governed by the oxygen evolution reaction (OER). In this work, we investigated the growth mechanism of CoFe hydroxide formed by in situ self-corrosion of iron foam for the first time and the significant influence of dissolved oxygen in the immersion solution on this process. Based on this, the CoP2-FeP4/IF heterostructure catalytic electrode demonstrates exceptional OER activity in a 1 M KOH electrolyte, with an overpotential of only 253 ± 4 mV (@10 mA cm-2), along with durability exceeding 1000 h. Density functional theory calculations indicate that constructing heterojunction interfaces promotes the redistribution of interface electrons, optimizing the free energy of adsorbed intermediate during the water oxidation process. This research highlights the importance of integrating self-corroding in-situ growth with interface engineering techniques to develop efficient water splitting materials.

Iron Doping of 2D Nickel-Based Metal-Organic Frameworks Enhances the Lattice Heterogeneous Interface Coupling Effect for Improved Electrocatalytic Oxygen Evolution

The coupling of lattice and heterostructure interfaces represents an effective strategy for disrupting the so-called scalar relationship and accelerating reactions involving multiple intermediates. In view of this, a lattice-heterostructure interfacial catalyst consisting of a crystalline Fe/Ni bimetallic MOF and amorphous Fe-MOF was designed in this paper for high-performance alkaline oxygen evolution reaction electrocatalysis. The strongly coupled lattice-heterostructure interface induces a unique synergistic effect that promotes electron transfer of the catalyst. The resulting catalyst exhibits exceptionally high catalytic activity for the oxygen evolution reaction in alkaline media, the Ni9Fe1-BDC-1@Fe-MOF coated on a glassy carbon electrode has an overpotential of 257 mV at a current density of 10 mA cm-2. Furthermore, this catalyst demonstrates a high electrochemical stability. These research results highlight the superiority of lattice-heterostructure interfaces in the development of advanced catalysts.

Efficient Electrocatalytic Hydrodechlorination and Detoxification of Chlorophenols by Palladium-Palladium Oxide Heterostructure

Electrocatalytic hydrodechlorination is a promising approach for simultaneous pollutant purification and valorization. However, the lack of electrocatalysts with high catalytic activity and selectivity limits its application. Here, we propose a palladium-palladium oxide (Pd-PdO) heterostructure for efficient electrocatalytic hydrodechlorination of recalcitrant chlorophenols and selective formation of phenol with superior Pd-mass activity (1.35 min-1 mgPd-1), which is 4.4 times of commercial Pd/C and about 10-100 times of reported Pd-based catalysts. The Pd-PdO heterostructure is stable in real water matrices and achieves selective phenol recovery (>99%) from the chlorophenol mixture and efficient detoxification along chlorophenol removal. Experimental results and computational modeling reveal that the adsorption/desorption behaviors of zerovalent Pd and PdO sites in the Pd-PdO heterostructure are optimized and a synergy is realized to promote atomic hydrogen (H*) generation, transfer, and utilization: H* is efficiently generated at zerovalent Pd sites, transferred to PdO sites, and eventually consumed in the dechlorination reaction at PdO sites. This work provides a promising strategy to realize the synergy of Pd with different valence states in the metal-metal oxide heterostructure for simultaneous decontamination, detoxification, and resource recovery from halogenated organic pollutants.

Promoting Water Oxidation by Proton Acceptable Groups Surrounding Catalyst on Electrode Surface

Large-scale hydrogen production through water splitting represents an optimal approach for storing sustainable but intermittent energy sources. However, water oxidation, a complex and sluggish reaction, poses a significant bottleneck for water splitting efficiency. The impact of outer chemical environments on the reaction kinetics of water oxidation catalytic centers remains unexplored. Herein, chemical environment impacts were integrated by featuring methylpyridinium cation group (Py+) around the classic Ru(bpy)(tpy) (bpy=2,2'-bipyridine, tpy=2,2' : 6',2''-terpyridine) water oxidation catalyst on the electrode surface via electrochemical co-polymerization. The presence of Py+ groups could significantly enhance the turnover frequencies of Ru(bpy)(tpy), surpassing the performance of typical proton acceptors such as pyridine and benzoic acid anchored around the catalyst. Mechanistic investigations reveal that the flexible internal proton acceptor anions induced by Py+ around Ru(bpy)(tpy) are more effective than conventionally anchored proton acceptors, which promoted the rate-determining proton transfer process and enhanced the rate of water nucleophilic attack during O-O bond formation. This study may provide a novel perspective on achieving efficient water oxidation systems by integrating cations into the outer chemical environments of catalytic centers.

Self-assembled hole transport engineering and bio-inspired coordination/incoordination ligands synergizing strategy for productive photoelectrochemical water splitting

Charge transport and metal site stability play a critical role on realizing efficient solar water splitting in photoelectrochemical devices. Here, we investigated BiVO4-based composite photoanodes (labelled as NF@PTA/2PACz/BVO) in which BiVO4, [2-(9H-carbazol-9-yl) ethyl] phosphonic acid (2PACz) hole transport layers based on self-assembled monolayers (SAMs), and terephthalic acid (PTA)-functionalized NiFeOOH (NF@PTA) oxygen evolution cocatalysts (OECs) structurally similar to the OECs in natural photosystem II, were assembled sequentially. Alignment of energy levels and stabilization of metal sites can be achieved by this layer-designed structure. And the uncoordinated (COOH) carboxylate groups can accelerate the proton transfer. Fundamental investigations reveal that the NF@PTA/2PACz/BVO photoanode exhibits unique properties including passivated surface traps, excellent carrier density and lifetime, enlarged photovoltage, and smoother hole transport band structure. Consequently, the optimum NF@PTA/2PACz/BVO photoanode shows the photoelectrochemical (PEC) performance of 5.43 mA cm-2 at 1.23 V vs reversible hydrogen electrode with an applied bias photon-to-current efficiency of 1.45 %. The coupled COFe bond between the coordinating carboxylate and the metals not only inhibits the leaching of the metal species but also maintains a steady photocurrent density over 20 h of stability test. Our work paves the way for the development of more efficient PEC cells with superior charge separation and breakthroughs in the stability of metal active sites, thus broadening their potential applications.

Tantalum-induced reconstruction of nickel sulfide for enhanced bifunctional water splitting: Separate activation of the lattice oxygen oxidation and hydrogen spillover

Designing highly active and stable bifunctional catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions is crucial for sustainable overall water splitting. Herein, we present a targeted reconstruction of Ni3S2 by introducing tantalum, achieving remarkable overall water splitting performance through the separate activation of the lattice oxygen mechanism and hydrogen spillover. Electrochemical Mass Spectrometry and in-situ Raman spectroscopy reveal that tantalum induces Ni3S2 to reconstruct into nickel hydroxide during OER, thereby enhancing catalytic activity via the activation of the lattice oxygen mechanism. In the corresponding HER, tantalum promotes the reconstruction of Ni3S2 into oxysulfide, facilitates hydrogen spillover, and acts as an anchor to shorten the spillover distance, improving the HER catalytic performance, as verified by the kinetic isotope effect and theoretical calculations. Therefore, the catalyst-based anion exchange membrane water electrolyzer system achieves a current density of 1 A cm-2 at just 1.97 V, maintaining continuous operation for 500 h. This study offers new insights into the design of bifunctional catalysts, advancing the development of efficient and robust overall water splitting catalysts.

Ultrafast Quasi-Solid-State Microwave Construction of Spongy Cobalt-Molybdenum Phosphide for Hydrogen Production Over Wide pH Range

The developed strategies for synthesizing metal phosphides are usually cumbersome and pollute the environment. In this work, an ultrafast (30 s) quasi-solid-state microwave approach is developed to construct cobalt-molybdenum phosphide decorated with Ru (Ru/CoxP-MoP) featured porous morphology with interconnected channels. The specific nanostructure favors mass transport, such as electrolyte bubbles transfer and exposing rich active sites. Moreover, the coupling effects between metallic elements, especially the decorated Ru, also act as a pivotal role on enhancing the electrocatalytic performance. Benefiting from the effects of composition and specific nanostructure, the prepared Ru/CoxP-MoP exhibits efficient HER performance with a current density of 10 mA cm-2 achieved in 1 m KOH, 0.5 m H2SO4, seawater containing 1 m KOH and 1 m PBS, with overpotentials of 52, 59, 55, 90 mV, and coupling with good stability. This work opens a novel and fast avenue to design metal-phosphide-based nanomaterials in energy-conversion and storage fields.

Tailoring the Heterointerfaces of Earth-Abundant Transition-Metal Nanoclusters on Nickel Oxide Nanosheets for Enhanced Overall Water Splitting through Electronic Structure Optimization

Evolving highly competent and economical electrocatalysts for alkaline water electrolysis is crucial in renewable hydrogen energy technologies. The slow hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) kinetics under alkaline electrolytes, still, has troubled developments in high-performance green hydrogen production systems. Herein, we demonstrate the tailoring of the interface of earth-abundant transition-metal nanoclusters (MNCs), including iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) nanoclusters on nickel oxide nanosheets (M NCs|NiO NS) through metal-support interaction for enriched overall water splitting under an alkaline electrolyte. The strong metal-metal oxide interaction allows alteration of the binding capabilities of hydrogen ions (*H) and hydroxyl ions (*OH) on Ni electrodes. Specifically, the robust interaction between Fe and NiO reveals optimized binding of H* and OH* energies, facilitating the water-splitting reaction under an alkaline electrolyte. In addition, the improved HER/OER catalytic activity is attained with the Fe NCs|NiO NS with small overpotentials of ∼62.0 and ∼380.0 mV for the HER and OER, respectively, a high mass activity of ∼90.0 A g-1, a turnover frequency of ∼5.94 s-1, and long-lasting stability via offering abundant electrochemical active sites, three-dimensional (3D) morphologies, and high dispersion of nanoclusters that provide effective charge and mass transport processes. This study provides a promising strategy for the effective design of efficient bifunctional electrocatalysts based on earth-abundant materials for alkaline water electrolyzers.

Ultrafast Room-Temperature Synthesis of Phosphate-Intercalated NiFe Layered Double Hydroxides for High-Performance Alkaline Seawater Oxidation

Quick and easy synthetic methods and highly efficient catalytic performance are equally important to anodic oxygen evolution reaction (OER) electrocatalysts for alkaline seawater electrolysis. Herein, we report a facile one-step route to in situ growing PO43- intercalated NiFe layered double hydroxides (NiFe-LDH) on Ni foam (denoted as NiFe-P/NF) by a room-temperature immersion for several minutes. This ultrafast approach transforms the NF surface into a rough PO43- intercalated NiFe-LDH overlayer, which demonstrates outstanding OER performance in both alkaline simulated and natural seawaters owing to good hydrophilic interface and the electrostatic repulsion of PO43- against Cl- anions. Density functional theory calculations reveal that the intercalated PO43- can not only promote electron transfer but also prevent Cl- from entering the interlayer and simultaneously inhibit the migration of Cl- over the NiFe-LDH surface. In alkaline simulated and natural seawater electrolytes, NiFe-P/NF needs low overpotentials of 248 and 298 mV to achieve a current density of 100 mA cm-2, respectively. NiFe-P/NF can stably run over 42 h in an alkaline high-salty electrolyte (1 M KOH + 2.5 M NaCl) at 250 mA cm-2, more than 70 times that of NiFe/NF (0.6 h), emphasizing the critical role of the intercalated PO43- anions on the excellent durability. This study offers a new strategy to modify commercial NF to prepare efficient and stable OER catalysts for seawater electrolysis.

The dual-functional role of carboxylate in a nickel-iron catalyst towards efficient oxygen evolution

The efficiency of the oxygen evolution reaction (OER) is severely limited by the sluggish proton-coupled electron transfer processes and inadequate long-term stability. Herein, we introduce a carboxylate group (TPA) to modify NiFe layered double hydroxide (NiFe LDH@TPA), resulting in notable improvements in both activity and stability. A combination of spectroscopic and theoretical investigations reveals the dual-functional role of incorporated TPA. It facilitates the deprotonation of OER intermediates while strengthening the Fe-O bond and acting as a molecular fence, ensuring superior OER kinetics and anti-dissolution properties. NiFe LDH@TPA delivers a low overpotential of 200 mV at 10 mA cm-2 and an impressive long-term stability of 500 h at 150 mA cm-2, significantly outperforming its unmodified counterpart. Furthermore, operating in an anion exchange membrane water electrolyzer, it affords prolonged stability at an industrial-scale current density of 1 A cm-2, sustaining performance for over 120 hours. This strategy offers a promising avenue for the development of durable and efficient OER catalysts.

Interfacial Regulation of Rice-Grain-like Iron-Nickel Phosphide Nanorods on Phosphorus-Doped Graphene Architectures as Bifunctional Electrocatalysts for Water Splitting

The design of bimetallic metal-organic frameworks (MOFs) with a hierarchical structure is important to improve the electrocatalytic performance of catalysts due to their synergistic effect on different metal ions. In this work, the catalyst comprises bimetallic iron-nickel MOF-derived FeNi phosphides, intricately integrated with phosphorus-doped reduced graphene oxide architectures (FeNi2P-C/P-rGA) through the hydrothermal and phosphating treatments. The hierarchical architecture of the catalyst is beneficial for exposing active sites and facilitating electron transfer. The FeNi2P-C/P-rGA catalyst exhibits excellent performance in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolytes. Notably, FeNi2P-C/P-rGA requires only the overpotential of 93 and 210 mV to achieve a current density of 10 mA cm-2 for the HER and OER with small values of Tafel slope and charge transfer resistance, respectively. Furthermore, the catalyst exhibits boosted activity for overall water splitting with a low potential of 1.56 V. This work can be considered to extend the design of multilevel catalysts in the application of water splitting.

Boosting Electrochemical Nitrate Reduction at Low Concentrations Through Simultaneous Electronic States Regulation and Proton Provision

Electrochemically converting nitrate (NO3 -) into ammonia (NH3) has emerged as an alternative strategy for NH3 production and effluent treatment. Nevertheless, the electroreduction of dilute NO3 - is still challenging due to the competitive adsorption between various aqueous species and NO3 -, and unfavorable water dissociation providing *H. Herein, a new tandem strategy is proposed to boost the electrochemical nitrate reduction reaction (NO3RR) performance of Cu nanoparticles supported on single Fe atoms dispersed N-doped carbon (Cu@Fe1-NC) at dilute NO3 - concentrations (≤100 ppm NO3 --N). The optimized Cu@Fe1-NC presents a FENH3 of 97.7% at -0.4 V versus RHE, and a significant NH3 yield of 1953.9 mmol h-1 gCu -1 at 100 ppm NO3 --N, a record-high activity for dilute NO3RR. The metal/carbon heterojunctions in Cu@Fe1-NC enable a spontaneous electron transfer from Cu to carbon substrate, resulting in electron-deficient Cu. As a result, the electron-deficient Cu facilitates the adsorption of NO3 - compared with the pristine Cu. The adjacent atomic Fe sites efficiently promote water dissociation, providing abundant *H for the hydrogenation of *NOx e at Cu sites. The synergistic effects between Cu and single Fe atom sites simultaneously decrease the energy barrier for NO3 - adsorption and hydrogenation, thereby enhancing the overall activity of NO3 - reduction.

Rational Design of Earth-Abundant Catalysts toward Sustainability

Catalysis is crucial for clean energy, green chemistry, and environmental remediation, but traditional methods rely on expensive and scarce precious metals. This review addresses this challenge by highlighting the promise of earth-abundant catalysts and the recent advancements in their rational design. Innovative strategies such as physics-inspired descriptors, high-throughput computational techniques, and artificial intelligence (AI)-assisted design with machine learning (ML) are explored, moving beyond time-consuming trial-and-error approaches. Additionally, biomimicry, inspired by efficient enzymes in nature, offers valuable insights. This review systematically analyses these design strategies, providing a roadmap for developing high-performance catalysts from abundant elements. Clean energy applications (water splitting, fuel cells, batteries) and green chemistry (ammonia synthesis, CO2 reduction) are targeted while delving into the fundamental principles, biomimetic approaches, and current challenges in this field. The way to a more sustainable future is paved by overcoming catalyst scarcity through rational design.

Electrosynthesis of Transition Metal Coordinated Polymers for Active and Stable Oxygen Evolution

Transition metal coordination polymers (TM-CP) are promising inexpensive and flexible electrocatalysts for oxygen evolution reaction in water electrolysis, while their facile synthesis and controllable regulation remain challenging. Here we report an anodic oxidation-electrodeposition strategy for the growth of TM-CP (TM=Fe, Co, Ni, Cr, Mn; CP=polyaniline, polypyrrole) films on a variety of metal substrates that act as both catalyst supports and metal ion sources. An exemplified bimetallic NiFe-polypyrrole (NiFe-PPy) features superior mechanical stability in friction and exhibits high activity with long-term durability in alkaline seawater (over 2000 h) and anion exchange membrane electrolyzer devices at current density of 500 mA cm-2. Spectroscopic and microscopic analysis unravels the configurations with atomically distributed metal sites induced by d-π conjugation, which transforms into a mosaic structure with NiFe (oxy)hydroxides embedded in PPy matrix during oxygen evolution. The superior catalytic performance is ascribed to the anchoring effect of PPy that inhibits metal dissolution, the strong substrate-to-catalyst interaction that ensures good adhesion, and the Fe/Ni-N coordination that modulates the electronic structures to facilitate the deprotonation of *OOH intermediate. This work provides a general strategy and mechanistic insight into building robust inorganic/polymer composite electrodes for oxygen electrocatalysis.

Tandem Proton Transfer in Carboxylated Supramolecular Polymer for Highly Efficient Overall Photosynthesis of Hydrogen Peroxide

Proton supply is as critical as O2 activation for artificial photosynthesis of hydrogen peroxide (H2O2) via two-electron oxygen reduction reaction (2e- ORR). However, proton release via water dissociation is frequently hindered because of the sluggish water oxidation reaction (WOR), extremely limiting the efficiency of photocatalytic H2O2 production. To tackle this challenge, carboxyl-enriched supramolecular polymer (perylene tetracarboxylic acid-PTCA) is elaborately prepared by molecular self-assembly for overall photosynthesis of H2O2. Interestingly, the interconversion between carboxyl as Brønsted acid and its conjugated base realizes rapid proton circulation. Through this efficient tandem proton transfer process, the spatial effect of photocatalytic reduction and oxidation reaction is greatly enhanced with reduced reaction barrier. This significantly facilitates 2e- photocatalytic ORR to synthesize H2O2 and in the meanwhile promotes 4e- photocatalytic WOR to evolve O2. Consequently, the as-developed PTCA exhibits a remarkable H2O2 yield of 185.6 μM h-1 in pure water and air atmosphere under visible light illumination. More impressively, an appreciable H2O2 yield of 78.6 μM h-1 can be well maintained in an anaerobic system owing to in situ O2 generation by 4e- photocatalytic WOR. Our study presents a novel concept for artificial photosynthesis of H2O2 via constructing efficient proton transfer pathway to enable rapid proton circulation.

Cluster-Level Heterostructure of PMo12/Cu for Efficient and Selective Electrocatalytic Hydrogenation of High-Concentration 5-Hydroxymethylfurfural

Electrochemical hydrogenation of aldehyde molecules, exemplified by 5-hydroxymethylfurfural (HMF), offers a sustainable approach for synthesizing higher value-added alcohols. However, severe coupling side reactions impede its practical implementation at high concentrations. In this work, a cluster-level heterostructure of a PMo12/Cu catalyst is synthesized by loading Keggin-type phosphomolybdic acid (H3PMo12O40, PMo12) onto Cu nanowires. The catalyst exhibits high selectivity in electrocatalytic hydrogenation (ECH) of HMF to 2,5-bishydroxymethylfuran (BHMF) under an unprecedentedly high substrate concentration of 1.0 M. Under -0.3 V (vs RHE) with 1.0 M HMF, PMo12/Cu shows a Faradaic efficiency as high as 98% with an excellent productivity of 4.35 mmol cm-2 h-1 toward BHMF, much higher than those on the pristine Cu nanowires. Mechanism studies and density functional theory calculations demonstrate that the heterostructural interface of PMo12/Cu serves as an active reaction center for the ECH. The unique electronic properties and geometric structure promote the dissociative reduction of water molecules to generate H* and reduce HMF with a decreased reaction energy barrier, which is responsible for exceptional reactivity and selectivity.

Promoting Oxygen Evolution Electrocatalysis by Coordination Engineering in Cobalt Phosphate

Understanding the structure-activity correlation is an important prerequisite for the rational design of high-efficiency electrocatalysts at the atomic level. However, the effect of coordination environment on electrocatalytic oxygen evolution reaction (OER) remains enigmatic. In this work, the regulation of proton transfer involved in water oxidation by coordination engineering based on Co3(PO4)2 and CoHPO4 is reported. The HPO4 2- anion has intermediate pKa value between Co(II)-H2O and Co(III)-H2O to be served as an appealing proton-coupled electron transfer (PCET) induction group. From theoretical calculations, the pH-dependent OER properties, deuterium kinetic isotope effects, operando electrochemical impedance spectroscopy (EIS) and Raman studies, the CoHPO4 catalyst beneficially reduces the energy barrier of proton hopping and modulates the formation energy of high-valent Co species, thereby enhancing OER activity. This work demonstrates a promising strategy that involves tuning the local coordination environment to optimize PCET steps and electrocatalytic activities for electrochemical applications. In addition, the designed system offers a motif to understand the structure-efficiency relationship from those amino-acid residue with proton buffer ability in natural photosynthesis.

Modifying Proton Relay into Bioinspired Dye-Based Coordination Polymer for Photocatalytic Proton-Coupled Electron Transfer

Proton-coupled electron transfer (PCET) imparts an energetic advantage over single electron transfer in activating inert substances. Natural PCET enzyme catalysis generally requires tripartite preorganization of proton relay, substrate-bound active center, and redox mediator, making the processes efficient and precluding side reactions. Inspired by this, a heterogeneous photocatalytic PCET system was established to achieve higher PCET driving forces by modifying proton relays into anthraquinone-based anionic coordination polymers. The proximally separated proton relays and photoredox-mediating anthraquinone moiety allowed pre-assembly of inert substrate between them, merging proton and electron into unsaturated bonds by photoreductive PCET, which enhanced reaction kinetics compared with the counter catalyst without proton relay. This photocatalytic PCET method was applied to a broad-scoped reduction of aryl ketones, unsaturated carbonyls, and aromatic compounds. The distinctive regioselectivities for the reduction of isoquinoline derivatives were found to occur on the carbon-ring sides. PCET-generated radical intermediate of quinoline could be trapped by alkene for proton relay-assisted Minisci addition, forming the pharmaceutical aza-acenaphthene scaffold within one step. When using heteroatom(X)-H/C-H compounds as proton-electron donors, this protocol could activate these inert bonds through photooxidative PCET to afford radicals and trap them by electron-deficient unsaturated compounds, furnishing the direct X-H/C-H functionalization.

Impact of Organic Anions on Metal Hydroxide Oxygen Evolution Catalysts

Structural metamorphosis of metal-organic frameworks (MOFs) eliciting highly active metal-hydroxide catalysts has come to the fore lately, with much promise. However, the role of organic ligands leaching into electrolytes during alkaline hydrolysis remains unclear. Here, we elucidate the influence of organic carboxylate anions on a family of Ni or NiFe-based hydroxide type catalysts during the oxygen evolution reaction. After excluding interfering variables, i.e., electrolyte purity, Ohmic loss, and electrolyte pH, the experimental results indicate that adding organic anions to the electrolyte profoundly impacts the redox potential of the Ni species versus with only a negligible effect on the oxygen evolution activities. In-depth studies demonstrate plausible reasons behind those observations and allude to far-reaching implications in controlling electrocatalysis in MOFs, mainly where compositional modularity entails fine-tuning organic anions.

Molecular Wiring of Electrocatalytic Nitrate reduction to Ammonia and Water Oxidation by Iron-Coordinated Macroporous Conductive Networks

Developing stable electrocatalysts with accessible isolated sites is desirable but highly challenging due to metal agglomeration and low surface stability of host materials. Here we report a general approach for synthesis of single-site Fe electrocatalysts by integrating a solvated Fe complex in conductive macroporous organic networks through redox-active coordination linkages. Electrochemical activation of the electrode exposes high-density coordinately unsaturated Fe sites for efficient adsorption and conversion of reaction substrates such as NO3 - and H2O. Using the electrode with isolated active Fe sites, electrocatalytic NO3 - reduction and H2O oxidation can be coupled in a single cell to produce NH3 and O2 at Faradaic efficiencies of 97 % and 100 %, respectively. The electrode exhibits excellent robustness in electrocatalysis for 200 hours with small decrease in catalytic efficiencies. Both the maximized Fe-site efficiency and the microscopic localization effect of the conductive organic matrix contribute to the high catalytic performances, which provides new understandings in tuning the efficiencies of metal catalysts for high-performance electrocatalytic cells.

The Electrocatalytic Activity of Au Electrodes Changes Significantly in Various Na+/K+ Supporting Electrolyte Mixtures

The potential of maximum entropy (PME) is an indicator of extreme disorder at the electrode/electrolyte interface and can predict changes in catalytic activity within electrolytes of varying compositions. The laser-induced current transient technique is employed to evaluate the PME for Au polycrystalline (Aupc) electrodes immersed in Ar-saturated cation electrolyte mixtures containing potassium and sodium ions at pH = 8. Five cation ratios (0.5 M K2SO4:0.5 M Na2SO4 = 0:1, 0.25:0.75, 0.5:0.5, 0.75:0.25, and 1:0) are explored, considering earlier studies that unveil cation-dependent shifts at near-neutral pH. Moreover, for all electrolyte compositions, electrochemical impedance spectroscopy is utilized to determine the double-layer capacitance (C DL), the minimum of which should be close to the potential of zero charge (PZC). By correlating cation molar ratios with the PMEs and PZCs, the impact on the model oxygen reduction reaction (ORR) activity, assessed via the rotating disk electrode method, is analyzed. The results demonstrate a linear relationship between electrolyte cation mixtures and PME, while ORR activity exhibits an exponential trend. This observation validates the PME-activity link hypothesis, underscoring electrolyte components' pivotal role in tailoring interfacial properties for electrocatalytic systems. These findings introduce a new degree of freedom for designing optimal electrocatalytic systems by adjusting various electrolyte components.

Emerging Doped Metal-Organic Frameworks: Recent Progress in Synthesis, Applications, and First-Principles Calculations

Metal-organic frameworks (MOFs) are crystalline porous materials with a long-range ordered structure and excellent specific surface area and have found a wide range of applications in diverse fields, such as catalysis, energy storage, sensing, and biomedicine. However, their poor electrical conductivity and chemical stability, low capacity, and weak adhesion to substrates have greatly limited their performance. Doping has emerged as a unique strategy to mitigate the issues. In this review, the concept, classification, and characterization methods of doped MOFs are first introduced, and recent progress in the synthesis and applications of doped MOFs, as well as the rapid advancements and applications of first-principles calculations based on the density functional theory (DFT) in unraveling the mechanistic origin of the enhanced performance are summarized. Finally, a perspective is included to highlight the key challenges in doping MOF materials and an outlook is provided on future research directions.

Stabilizing atomic Ru species in conjugated sp2 carbon-linked covalent organic framework for acidic water oxidation

Suppressing the kinetically favorable lattice oxygen oxidation mechanism pathway and triggering the adsorbate evolution mechanism pathway at the expense of activity are the state-of-the-art strategies for Ru-based electrocatalysts toward acidic water oxidation. Herein, atomically dispersed Ru species are anchored into an acidic stable vinyl-linked 2D covalent organic framework with unique crossed π-conjugation, termed as COF-205-Ru. The crossed π-conjugated structure of COF-205-Ru not only suppresses the dissolution of Ru through strong Ru-N motifs, but also reduces the oxidation state of Ru by multiple π-conjugations, thereby activating the oxygen coordinated to Ru and stabilizing the oxygen vacancies during oxygen evolution process. Experimental results including X-ray absorption spectroscopy, in situ Raman spectroscopy, in situ powder X-ray diffraction patterns, and theoretical calculations unveil the activated oxygen with elevated energy level of O 2p band, decreased oxygen vacancy formation energy, promoted electrochemical stability, and significantly reduced energy barrier of potential determining step for acidic water oxidation. Consequently, the obtained COF-205-Ru displays a high mass activity with 2659.3 A g-1, which is 32-fold higher than the commercial RuO2, and retains long-term durability of over 280 h. This work provides a strategy to simultaneously promote the stability and activity of Ru-based catalysts for acidic water oxidation.

Manipulating the Rate and Overpotential for Electrochemical Water Oxidation: Mechanistic Insights for Cobalt Catalysts Bearing Noninnocent Bis(benzimidazole)pyrazolide Ligands

Electrochemical water oxidation is known as the anodic reaction of water splitting. Efficient design and earth-abundant electrocatalysts are crucial to this process. Herein, we report a family of catalysts (1-3) bearing bis(benzimidazole)pyrazolide ligands (H 2 L1-H 2 L3). H 2 L3 contains electron-donating substituents and noninnocent components, resulting in catalyst 3 exhibiting unique performance. Kinetic studies show first-order kinetic dependence on [3] and [H2O] under neutral and alkaline conditions. In contrast to previously reported catalyst 1, catalyst 3 exhibits an insignificant kinetic isotope effect of 1.25 and zero-order dependence on [NaOH]. Based on various spectroscopic methods and computational findings, the L3Co2 III(μ-OH) species is proposed to be the catalyst resting state and the nucleophilic attack of water on this species is identified as the turnover-limiting step of the catalytic reaction. Computational studies provided insights into how the interplay between the electronic effect and ligand noninnocence results in catalyst 3 acting via a different reaction mechanism. The variation in the turnover-limiting step and catalytic potentials of species 1-3 leads to their catalytic rates being independent of the overpotential, as evidenced by Eyring analysis. Overall, we demonstrate how ligand design may be utilized to retain good water oxidation activity at low overpotentials.