Strong p-d Orbital Hybridization on Bismuth Nanosheets for High Performing CO2 Electroreduction

Electronic Modulation of Bismuth by g-C3N4 Constructs Electron-Enriched Active Sites for Accelerated CO2 Electroreduction to Formate

Electrochemical reduction of CO2 (ECO2RR) to formate represents a promising approach to achieving carbon neutrality, yet it faces significant challenges due to the low adsorption efficiency of the CO2 intermediates. In this study, we developed a highly dispersed electron-rich Bi metal catalyst, utilizing low-cost g-C3N4 as a nonmetallic support and electron donor. This design created a conductive network and a multielectron environment around the Bi atoms that facilitated dynamic interfacial charge transfer from g-C3N4 to Bi, thus enhancing the catalytic efficiency of active sites. The assembly catalyst exhibited a formate selectivity of over 90% within a wide potential window and maintained stable catalytic activity in simulated seawater solutions. In situ Raman spectroscopy and DFT calculations indicated that the incorporation of the nonmetallic support shifted the Bi-p band center to more negative values while increasing Bader charge transfer between Bi and *OCHO intermediates. This indicated enhanced adsorption of the *OCHO intermediate by electron-rich Bi, thus improving the selectivity and activity for formate production.

In Situ/Operando Characterization Techniques for Reaction Interface in Electrocatalytic CO2 Reduction

CO2 reduction reaction (CO2RR) has attracted considerable attention as a sustainable approach for carbon capture and conversion. However, the dynamic nature of electrocatalysts under operational conditions, particularly at the reaction interface, presents significant challenges for understanding reaction mechanisms and optimizing catalyst design. In situ/operando characterization techniques are crucial to understanding the reaction interfaces and mechanisms of CO2RR. This review focuses on various in situ/operando techniques employed to explore reaction interfaces, the insights derived from these studies, and their implications for catalyst design.

The Improved Covalent Coupling Induced by Bi Cations in CoBiSex Nanosheet Arrays for Stable Water Electrolysis

Transition metal selenides (TMSes) with high electrical conductivity, easily regulated morphological structure, and unique electronic structure have been explored as promising electrocatalysts for electrolytic water, while the lower intrinsic electrocatalytic capability has limited their wide application. Herein, we obtained CoSe nanosheet arrays with Bi cations incorporation (CoBiSex nanosheet arrays) driven by spinel oxides. Compared with spinel oxides, the low electronegativity of Se in CoBiSex nanosheet arrays leads to a portion of Co2+ in the low spin states (t2g6eg1) due to the high covalent interaction between Co and Se, which can facilitate charge transfer. Density functional theory (DFT) calculation results further identify the redistribution of electron density from Se to Co, intensifying the adsorption of OOH* during the electrolytic water process with a 140 h robust catalytic performance. This work offers a unique strategy for exploring TMSe materials and their potential applications in the electrolytic water process.

Elucidating the Functional Orbital Evolution in Transition Metal-Doped Bi3O4Br Platforms for CO2 Photoreduction

Frontier orbital hybridization plays a vital role in the initial adsorption and activation process during catalysis. A formidable challenge is the precise determination of active orbitals/sites. Herein, 2D Bi3O4Br nanosheets are adopted as an operable platform for heteroatom doping of various transition metals (Fe, Ni, Zn/Cd). As the atom number of dopants increases, the capability of selective CO2 photoconversion is continuously amplified. The intrinsic nature is the variation of active functional orbital as indicated from band center distance (Δd/p-p) indicators. The calculated charge transfer of various CO2-bound geometries further demonstrates the p-p orbital interaction overwhelms d-p orbital interaction. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy results verify the charged nature of Bi sites with 6p orbitals not fully filled by electrons. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis and Gibbs free energy change profile suggest the rapid emergence of the critical *COOH intermediate in a thermodynamically preferred pathway.

Structure-activity relationship of small organic molecule functionalized Bi-based heterogeneous catalysts for electrocatalytic reduction of CO2 to formate

Ligand engineering has proven to be an effective strategy for tuning and controlling the microenvironment of coordinated metal centers, highlighting the critical bridge between the activity and structural features of catalysts during electrocatalytic CO2 reduction reactions (eCO2RR). However, the limited availability of diverse organic ligands has hindered the development of novel high-performing electrocatalysts. In contrast, small organic molecules have been widely used in the fabrication of metal complexes due to their well-defined functionalities, low cost, and easy accessibility. Herein, functionalized small organic molecules were employed to prepare a new type of Bi-based heterogeneous molecular catalyst. These molecular catalysts enhance both electrical conductivity and catalytic activity for converting CO2 to formate in the eCO2RR. The relationship between the structure and electrochemical performance of organic-functionalized Bi-based heterogeneous catalysts was thoroughly investigated. Comprehensive characterization and kinetic studies demonstrated that the functional groups of the organic molecules construct bond pathways for electron transfer and promote the transformation of the active phase from Bi to Bi2O2CO3. In-situ Raman spectroscopy reveal that the organic molecules remain intact during the structural reorganization, which is beneficial for the sustained generation of Bi2O2CO3 active site during the eCO2RR process. Consequently, the organic functionalized Bi-based catalysts achieved a high formate Faradaic efficiency (FEHCOO-) of 89.8 % and a high current density (jHCOO-) of 40.0 mA cm-2 at a potential of -0.95 V vs. RHE in an H-type cell. This work establishes a novel strategy for creating active heterogeneous catalysts using small organic molecules, opening new avenues for the development of efficient electrocatalysts for CO2 reduction.

V activated electro-epoxidation catalyst in membrane electrode assembly system for the production of propylene oxide

Direct electro-epoxidation of propylene (D-EOPO) with a membrane electrode assembly (MEA) system represents a sustainable approach for producing propylene oxide, which can reduce ohmic losses and simplify product separation. To address the challenges of selectivity and activity, we develop an Ag/V catalyst and integrate it into the "liquid-free" MEA reactor for continues D-EOPO. The V in the catalyst facilitates the formation of Ag-O active centers, thereby reducing the generation energy of *O radicals. Meanwhile, V doping also results in a downshift of the d-band center of the Ag sites. Consequently, the formation of the crucial intermediate (*OC3H6) is significantly accelerated through the coupling *O with adsorbed propylene, thereby markedly improving propylene oxide (PO) production. The MEA reactor, integrated with the developed Ag/V catalyst, can maintain a stable production rate of PO at 227 μmol/h over a period of 78 hours. Thus, the "liquid-free" electro-epoxidation protocol developed here exhibits greater industrial applicability.

Intermetallic PtSn Nanosheets with p-d Orbital Hybridization for Selective Hydroxylamine Electrosynthesis

The electrocatalytic nitrate reduction to hydroxylamine (NH2OH) is a challenging catalytic process that has gained significant attention. However, its performance is hindered by the low selectivity of the electrocatalysts. Here, intermetallic PtSn nanosheets with p-d orbital hybridization have been synthesized, which significantly enhances the performance of electrocatalytic nitrate reduction to NH2OH. The Faradaic efficiency of NH2OH reaches a maximum of 82.83 ± 1.55% at -0.10 V versus the reversible hydrogen electrode (vs RHE), and the yield of NH2OH achieves 6.15 ± 0.32 mmol h-1 mgcat-1 at -0.25 V vs RHE. Mechanistic studies reveal that p-d orbital hybridization between p-block Sn and d-block Pt effectively enhances nitrate adsorption and NH2OH desorption to boost electrochemical NH2OH synthesis. Given their excellent performance in the electrochemical synthesis of NH2OH, PtSn nanosheets are utilized as the cathode in an alkaline-acid hybrid Zn-NO3- battery to facilitate the production of NH2OH, achieving an NH2OH FE of 80.42%.

Oxygen Evolution Reaction of Amorphous/Crystalline Composites of NiFe(OH)x/NiFe2O4

Orbital structures are strongly correlated with catalytic performance, whereas their regulation strategy is still in pursuit. Herein, the Fe 3d and O 2p orbital hybridization was optimized by controlling the content of amorphous NiFe(OH)x (a-NiFe(OH)x), which was grown in situ on crystalline NiFe2O4 (c-NiFe2O4) using an ultrasonic reduction method. The results of electron energy loss spectroscopy (EELS) and X-ray absorption spectra (XAS) revealed that the Fe-Oa orbital hybridization in a-NiFe(OH)x is effectively strengthened by jointing with the adjacent oxygen (Oc) in c-NiFe2O4, which is further confirmed by the higher antibonding orbital energies based on density functional theory (DFT) calculations. The resultant Oa-Fe-Oc at the composite interface leads to balanced adsorption and desorption energies. Accordingly, the optimal composite with strong Fe 3d-O 2p hybridization results in enhanced OER performance, and the overpotential is 150 mV, lower than that of the pristine sample. This work represents a promising approach to orbital hybridization via the introduction of an amorphous phase to construct highly efficient catalysts.

In Situ Reconstructed Hydroxyl-Rich Atomic-Thin Bi2O2CO3 Enables Ampere-Scale Synthesis of Formate from CO2 with Activated Water Dissociation

Renewable electricity-driven CO2 electroreduction provides a promising route toward carbon neutrality and sustainable chemical production. Nevertheless, the viability of this route faces constraints of catalytic efficiency and durability in near-neutral electrolytes at industrial-scale current densities, mechanistically originating from unfavorable accommodation of *H species from water dissociation. Herein, a new strategy is reported to accelerate water dissociation by the rich surface hydroxyl on bismuth subcarbonate nanosheets in situ electrochemical transformed from bismuth hydroxide nanotube precursors. This catalyst enables the electrosynthesis of formate at current densities up to 1000 mA cm-2 with >96% faradaic efficiencies in flow cells, and a 200 h durable membrane electrode assembly in a dilute near-neutral environment. Combined kinetic studies, in situ characterizations, and theoretical calculations reveal that the atomic thickness strengthens the hydroxyl adsorption, and with a highly localized electron configuration, the hydroxyl-functionalized surface is more affinitive to oxygenated species, thus lowering the barrier for water dissociation and the crucial hydrogenation step in the proton-coupled electron transfer from *OCHO to *HCOOH.

Strengthened d-p orbital hybridization and hydrogen diffusion in a hollow N-doped porous carbon/Ru cluster catalyst system for hydrogen evolution reactions

Developing advanced catalysts with rapid hydrogen evolution reaction (HER) kinetics in alkaline media is vital for hydrogen production. Through the d-p orbital hybridization effect, the electronic structure and H* adsorption can be optimized on metal species. Herein, a N-doped hollow carbon (H-NPC)-supported Ru cluster (c-Ru@H-NPC) catalyst was constructed via carbonization of well-defined hollow metal-organic frameworks, followed by etching and anchoring of Ru clusters. The hollow structure could not alter the coordination number of Ru while exhibiting higher-level electron transfer, thereby strengthening the orbital hybridization. Additionally, finite element simulations indicated the acceleration of H2 diffusion for hollow structures. Furthermore, the N-doping strengthened the electron interaction of Ru-C by the d-p hybridization effect, which was confirmed by theoretical calculations and in situ Raman spectroscopy. Therefore, in alkaline/alkaline seawater media, c-Ru@H-NPC needed only 10/12 mV overpotentials and 1.52/1.55 V cell voltages to drive the HER and overall water splitting, respectively, at a current density of 10 mA cm-2, exhibiting outstanding catalytic activity. Meanwhile, the attenuation of current density was very small towards successive stability tests for >55 h at 10 mA cm-2. This work permits new insights into the design of high-performance metal cluster catalysts for the HER and other conversion reactions.

Solar energy powered electrochemical reduction of CO2 on In2O3 nanosheets with high energy conversion efficiency at a large current density

Electrochemical CO2 reduction (ECO2R) to value-added chemicals offers a promising approach to both mitigate CO2 emission and facilitate renewable energy conversion. We demonstrate a solar energy powered ECO2R system operating at a relatively large current density (57 mA cm-2) using In2O3 nanosheets (NSs) as the cathode and a commercial perovskite solar cell as the electricity generator, which achieves the high solar to formate energy conversion efficiency of 6.6 %. The significantly enhanced operative current density with a fair solar energy conversion efficiency on In2O3 NSs can be ascribed to their high activity and selectivity for formate production, as well as the fast kinetics for ECO2R. The Faradic efficiencies (FEs) of formate In2O3 NSs are all above 93 %, with the partial current density of formate ranging from 2.3 to 342 mA cm-2 in a gas diffusion flow cell, which is among the widest for formate production on In-based catalysts. In-situ Raman spectroscopy and density functional theory simulations reveal that the exceptional performances of formate production on In2O3 NSs originates from the presence of abundant low coordinated edge sites, which effectively promote the selective adsorption of *OCHO while inhibiting *H adsorption.

Bismuth oxide nanoflakes grown on defective microporous carbon endows high-efficient CO2 reduction at ampere level

Carbon dioxide electroreduction is a green technology for artificial carbon sequestration, which is being delayed from industrialization due to the lack of efficient catalysts at high current conditions. Herein, the Bi2O3 nanoflakes were uniformly grown on a defective porous carbon (PC). This self-assembling Bi2O3/PC catalyst was applied to drive CO2 electroreduction at 1.0 A, 1.5 A and 2.0 A while the Faradaic efficiency of formate reaches 91.50 %, 86.30 % and 84.22 %, respectively. Density functional theory calculations revealed the intrinsic defect of carbon is able to give electron to Bi through O bridge, which increased the electron aggregation of Bi and lowered the generation energy barrier of *OCHO intermediate. Additionally, the unique 3D network of staggered Bi2O3 enhances the CO2 adsorption and favors the electron transportation. By integrating all above advantages into a solid electrolyte-type cell, we are able to produce pure formic acid in a rate of 15.48 mmol h-1 at ampere current.

Integrated "Two-in-One" Strategy for High-Rate Electrocatalytic CO2 Reduction to Formate

The electrochemical CO2 reduction reaction (ECR) is a promising pathway to producing valuable chemicals and fuels. Despite extensive studies reported, improving CO2 adsorption for local CO2 enrichment or water dissociation to generate sufficient H* is still not enough to achieve industrial-relevant current densities. Herein, we report a "two-in-one" catalyst, defective Bi nanosheets modified by CrOx (Bi-CrOx), to simultaneously promote CO2 adsorption and water dissociation, thereby enhancing the activity and selectivity of ECR to formate. The Bi-CrOx exhibits an excellent Faradaic efficiency (≈100 %) in a wide potential range from -0.4 to -0.9 V. In addition, it achieves a remarkable formate partial current density of 687 mA cm-2 at a moderate potential of -0.9 V without iR compensation, the highest value at -0.9 V reported so far. Control experiments and theoretical simulations revealed that the defective Bi facilitates CO2 adsorption/activation while the CrOx accounts for enhancing the protonation process via accelerating H2O dissociation. This work presents a pathway to boosting formate production through tuning CO2 and H2O species at the same time.

Large-Current CO2 Electromethanation Through Active Hydrogen Regulation Over Carbon Nitride

Electromethanation of CO2 has received intensive attention due to its high calorific value and convenient storage along with transportation to accommodate industrial demands. However, it is limited by sluggish multi-step proton-coupled electron transfer kinetics and undesired *H coupling under high current density, posing great challenges to its commercialization. Herein, carbon nitride (CN) with superior hydrogen adsorption ability is used as an active-hydrogen adsorption and supply material. Through a facile liquid-assisted exfoliation and electrostatic self-assembly strategy to strengthen its interfacial contacts with Cu2O catalysts, yielding a strengthened CH4 production 52 times higher than that of pristine Cu2O. Flow-cell test ultimately achieved FECH4 and remarkably CH4 partial current density of 61% and 561 mA cm-2, respectively. With in situ ATR-FTIR spectra and DFT calculations, it is established that strengthened interfaces enabled abundant *H tethered by ─C─N═C─ sites in CN nanosheets and oriented to the *CO hydrogenation to *CHO and *CHx on Cu species. This work reveals the profound influence of fine-expanded interfaces with dimensional materials on the product distribution and yield through the active-hydrogen management, which is of reference value for other small-molecule electro-polarization dominated by the proton-coupled electron transfer (PCET) process (e.g., N2, O2, etc.).

Relationships between the Surface Hydrophilicity of a Bismuth Electrode and the Product Selectivity of Electrocatalytic CO2 Reduction

Two types of bismuth films (micro-Bi and nano-Bi) were prepared, and their electrocatalytic behavior was studied in terms of reduction current and product selectivity in a potential range of -0.776 to -1.376 V vs RHE. CO2 and H2O molecules competed with each other for reduction on the surfaces of both types of films, and formate and H2 were the respective major products of reductive reactions. Under the same conditions, nano-Bi exhibited lower selectivity for formate and higher selectivity for H2 compared to the respective micro-Bi cases with bismuth films of similar thickness. This can be attributed to the higher hydrophilicity of bismuth film surfaces of nano-Bi due to surface nanoscale roughness and lower surface-carbon content compared with those of micro-Bi. Our results suggest a new strategy for controlling the selectivity of electrocatalytic CO2 reduction under aqueous electrolytes through the use of surface engineering.

Progress in Catalysts for Formic Acid Production by Electrochemical Reduction of Carbon Dioxide

Utilising renewable energy to drive the conversion of carbon dioxide into more valuable products can effectively alleviate the energy crisis and protect the environment while actively responding to the policy of "carbon peaking and carbon neutrality". Additionally, formic acid/formate is one of the most promising and commercially valuable products of the electrocatalytic CO2 reduction reaction (ECO2RR) as well as a nonhazardous material for hydrogen storage. With the continuous progress in the field of electrocatalytic CO2 reduction to formic acid/formate (ECO2RF), various electrocatalysts with excellent performance have been developed. In this paper, first, the reaction mechanism of ECO2RF is briefly summarised, and then the recent research progress for various catalysts for ECO2RF, including metal-based catalysts, carbon-based material catalysts, metal-organic framework catalysts, covalent organic framework catalysts, and molecular catalysts, is reviewed. Finally, the current challenges and future perspectives of ECO2RF are discussed and presented.

Ultrafast Ion Transport in 2D Confined MXene for Improved Electrochemical Performance: Boron-Atom-Substituted -OH Termination

Regulating the surface termination of a confined space to achieve ultrafast ion transport remains an ongoing challenge. Two-dimensional (2D) MXenes possess adjustable structures and interlayer spacing, which provide an ideal platform for in-depth investigation of ion transport in 2D confined space; however, the strong interaction of the negatively charged terminations in MXenes hinders the transport of intercalated cations. In this work, we proposed a strategy that precisely regulates the surface modification of Ti3C2Tx MXene with the weak polarity of boron atoms (SCB-MXene) via the distinct effect of supercritical CO2. This not only could effectively substitute -OH termination in MXene but also can prevent the loss of -O active sites, and then, both ultrafast ion transport and high volumetric capacitance can be achieved simultaneously. Ideally, a volumetric capacitance up to 742.7 C cm-3 at 1000 mV s-1 for the SCB-MXene film as pseudocapacitive materials that provides an energy density of 66.3 Wh L-1 even at an ultrahigh power density of 132.5 kW L-1 is obtained, which is a prominent record of energy density and power density reported up to now. Subsequently, it can be used in large-scale energy storage and conversion devices.

Inhibition effect of p-d orbital hybridized PtSn nanozymes for colorimetric sensor array of antioxidants

Rational design of peroxidase (POD)-like nanozymes with high activity and specificity still faces a great challenge. Besides, the investigations of nanozymes inhibitors commonly focus on inhibition efficiency, the interaction between nanozymes-involved catalytic reactions and inhibitors is rarely reported. In this work, we design a p-block metal Sn-doped Pt (p-d/PtSn) nanozymes with the selective enhancement of POD-like activity. The p-d orbital hybridization interaction between Pt and Sn can effectively optimize the electronic structure of PtSn nanozymes and thus selectively enhance POD-like activity. In addition, the antioxidants as nanozymes inhibitors can effectively inhibit the POD-like activity of p-d/PtSn nanozymes, which results in the fact that antioxidants absorbed on the p-d/PtSn surface can hinder the adsorption of hydrogen peroxide. The inhibition type (glutathione as a model molecule) is reversible mixed-inhibition with inhibition constants (Ki' and Ki) of 0.21 mM and 0.03 mM. Finally, based on the varying inhibition levels of antioxidant molecules, a colorimetric sensor array is constructed to distinguish and simultaneously detect five antioxidants. This work is expected to design highly active and specific nanozymes through p-d orbital hybrid engineering, and also provides insights into the interaction between nanozymes and inhibitors.

p-d Orbital Hybridization in Ag-based Electrocatalysts for Enhanced Nitrate-to-Ammonia Conversion

Considering the substantial role of ammonia, developing highly efficient electrocatalysts for nitrate-to-ammonia conversion has attracted increasing interest. Herein, we proposed a feasible strategy of p-d orbital hybridization via doping p-block metals in an Ag host, which drastically promotes the performance of nitrate adsorption and disassociation. Typically, a Sn-doped Ag catalyst (SnAg) delivers a maximum Faradaic efficiency (FE) of 95.5±1.85 % for NH3 at -0.4 V vs. RHE and reaches the highest NH3 yield rate to 482.3±14.1 mg h-1 mgcat. -1. In a flow cell, the SnAg catalyst achieves a FE of 90.2 % at an ampere-level current density of 1.1 A cm-2 with an NH3 yield of 78.6 mg h-1 cm-2, during which NH3 can be further extracted to prepare struvite as high-quality fertilizer. A mechanistic study reveals that a strong p-d orbital hybridization effect in SnAg is beneficial for nitrite deoxygenation, a rate-determining step for NH3 synthesis, which as a general principle, can be further extended to Bi- and In-doped Ag catalysts. Moreover, when integrated into a Zn-nitrate battery, such a SnAg cathode contributes to a superior energy density of 639 Wh L-1, high power density of 18.1 mW cm-2, and continuous NH3 production.

Surface Area-Enhanced Cerium and Sulfur-Modified Hierarchical Bismuth Oxide Nanosheets for Electrochemical Carbon Dioxide Reduction to Formate

Electrochemical carbon dioxide reduction reaction (ECO2RR) is a promising approach to synthesize fuels and value-added chemical feedstocks while reducing atmospheric CO2 levels. Here, high surface area cerium and sulfur-doped hierarchical bismuth oxide nanosheets (Ce@S-Bi2O3) are develpoed by a solvothermal method. The resulting Ce@S-Bi2O3 electrocatalyst shows a maximum formate Faradaic efficiency (FE) of 92.5% and a current density of 42.09 mA cm-2 at -1.16 V versus RHE using a traditional H-cell system. Furthermore, using a three-chamber gas diffusion electrode (GDE) reactor, a maximum formate FE of 85% is achieved in a wide range of applied potentials (-0.86 to -1.36 V vs RHE) using Ce@S-Bi2O3. The density functional theory (DFT) results show that doping of Ce and S in Bi2O3 enhances formate production by weakening the OH* and H* species. Moreover, DFT calculations reveal that *OCHO is a dominant pathway on Ce@S-Bi2O3 that leads to efficient formate production. This study opens up new avenues for designing metal and element-doped electrocatalysts to improve the catalytic activity and selectivity for ECO2RR.

Regulating the Critical Intermediates of Dual-Atom Catalysts for CO2 Electroreduction

Electrocatalysis is a very attractive way to achieve a sustainable carbon cycle by converting CO2 into organic fuels and feedstocks. Therefore, it is crucial to design advanced electrocatalysts by understanding the reaction mechanism of electrochemical CO2 reduction reaction (eCO2RR) with multiple electron transfers. Among electrocatalysts, dual-atom catalysts (DACs) are promising candidates due to their distinct electronic structures and extremely high atomic utilization efficiency. Herein, the eCO2RR mechanism and the identification of intermediates using advanced characterization techniques, with a particular focus on regulating the critical intermediates are systematically summarized. Further, the insightful understanding of the functionality of DACs originates from the variable metrics of electronic structures including orbital structure, charge distribution, and electron spin state, which influences the active sites and critical intermediates in eCO2RR processes. Based on the intrinsic relationship between variable metrics and critical intermediates, the optimized strategies of DACs are summarized containing the participation of synergistic atoms, engineering of the atomic coordination environment, regulation of the diversity of central metal atoms, and modulation of metal-support interaction. Finally, the challenges and future opportunities of atomically dispersed catalysts for eCO2RR processes are discussed.

Hydrogen Evolution Reactivity of Pentagonal Carbon Rings and p-d Orbital Hybridization Effect with Ru

Topological defects are inevitable existence in carbon-based frameworks, but their intrinsic electrocatalytic activity and mechanism remain under-explored. Herein, the hydrogen evolution reaction (HER) of pentagonal carbon-rings is probed by constructing pentagonal ring-rich carbon (PRC), with optimized electronic structures and higher HER activity relative to common hexagonal carbon (HC). Furthermore, to improve the reactivity, we couple Ru clusters with PRC (Ru@PRC) through p-d orbital hybridization between C and Ru atoms, which drives a shortcut transfer of electrons from Ru clusters to pentagonal rings. The electron-deficient Ru species leads to a notable negative shift in d-band centers of Ru and weakens their binding strength with hydrogen intermediates, thus enhancing the HER activity in different pH media. Especially, at a current density of 10 mA cm-2, PRC greatly reduces alkaline HER overpotentials from 540 to 380 mV. And Ru@PRC even exhibits low overpotentials of 28 and 275 mV to reach current densities of 10 and 1000 mA cm-2, respectively. Impressively, the mass activity and price activity of Ru@PRC are 7.83 and 15.7 times higher than that of Pt/C at the overpotential of 50 mV. Our data unveil the positive HER reactivity of pentagonal defects and good application prospects.

Steering Geometric Reconstruction of Bismuth with Accelerated Dynamics for CO2 Electroreduction

Bismuth-based materials have emerged as promising catalysts in the electrocatalytic reduction of CO2 to formate. However, the reasons for the reconstruction of Bi-based precursors to form bismuth nanosheets are still puzzling, especially the formation of defective bismuth sites. Herein, we prepare bismuth nanosheets with vacancy-rich defects (V-Bi NS) by rapidly reconstructing Bi19Cl3S27 under negative potential. Theoretical analysis reveals that the introduction of chlorine induces the generation of intrinsic electric field in the precursor, thereby increasing the electron transfer rate and further promoting the metallization of trivalent bismuth. Meanwhile, experimental tests verify that Bi19Cl3S27 has a faster reconstruction rate than Bi2S3. The formed V-Bi NS exhibits up to 96 % HCOO- Faraday efficiency and 400 mA cm-2 HCOO- partial current densities, and its electrochemical active surface area normalized formate current density and yield are 2.2 times higher than those of intact bismuth nanosheets (I-Bi NS). Density functional theory calculations indicate that bismuth vacancies with electron-rich aggregation reduce the activation energy of CO2 to *CO2 - radicals and stabilize the adsorption of the key intermediate *OCHO, thus facilitating the reaction kinetics of formate production.

Synergistic Effects of Doping and Strain in Bismuth Catalysts for CO2 Electroreduction

Doping is a recognized method for enhancing catalytic performance. The introduction of strains is a common consequence of doping, although it is often overlooked. Differentiating the impact of doping and strain on catalytic performance poses a significant challenge. In this study, Cu-doped Bi catalysts with substantial tensile strain are synthesized. The synergistic effects of doping and strain in bismuth result in a remarkable CO2RR performance. Under optimized conditions, Cu1/6-Bi demonstrates exceptional formate Faradaic efficiency (>95%) and maintains over 90% across a wide potential window of 900 mV. Furthermore, it delivers an industrial-relevant partial current density of -317 mA cm-2 at -1.2 VRHE in a flow cell, while maintaining its selectivity. Additionally, it exhibits exceptional long-term stability, surpassing 120 h at -200 mA cm-2. Through experimental and theoretical mechanistic investigations, it has been determined that the introduction of tensile strain facilitates the adsorption of *CO2, thereby enhancing the reaction kinetics. Moreover, the presence of Cu dopants and tensile strain further diminishes the energy barrier for the formation of *OCHO intermediate. This study not only offers valuable insights for the development of effective catalysts for CO2RR through doping, but also establishes correlations between doping, lattice strains, and catalytic properties of bismuth catalysts.

CuO (111) Microcrystalline Evoked Indium-Organic Framework for Efficient Electroreduction of CO2 to Formate

Electrochemical reduction of carbon dioxide (CO2RR) to formate is economically beneficial but suffers from poor selectivity and high overpotential. Herein, enriched microcrystalline copper oxide is introduced on the surface of indium-based metal-organic frameworks. Benefiting from the CuO (111) microcrystalline shell and formed catalytic active In-Cu interfaces, the obtained MIL-68(In)/CuO heterostructure display excellent CO2RR to formate with a Faradaic efficiency (FE) as high as 89.7% at low potential of only -0.7 V vs. RHE in a flow cell. Significantly, the membrane electrode assembly (MEA) cell based on MIL-68(In)/CuO exhibit a remarkable current density of 640.3 mA cm-2 at 3.1 V and can be stably operated for 180 h at 2.7 V with a current density of 200 mA cm-2. The ex/in situ electrochemical investigations reveal that the introduction of CuO increases the formation rate of the carbon dioxide reduction intermediate *HCOO- and inhibits the competitive hydrogen evolution reaction. This work not only provides an in-depth study of the mechanism of the CO2RR pathways on In/Cu composite catalyst but also offers an effective strategy for the interface design of electrocatalytic carbon dioxide reduction reaction.

Thermal-Driven Dispersion of Bismuth Nanoparticles among Carbon Matrix for Efficient Carbon Dioxide Reduction

The poor electrocatalytic stability and rapid deactivation of metal electrocatalysts are always present in the electrocatalytic conversion of carbon dioxide (CO2) due to the harsh reduction condition. Herein, we demonstrate the controllable dispersion of ultrafine bismuth nanoparticles among the hollow carbon shell (Bi@C-700-4) simply by a thermal-driven diffusion process. The confinement effect of nitrogen-doped carbon matrix is able to low the surface energy of bismuth nanoparticles against the easy aggregation commonly observed for the thermal treatment. On the basis of the synergistic effect and confinement effect between bismuth nanoparticles and carbon matrix, the highly dispersed active sites render the obviously improved electrocatalytic activity and stability for CO2 reduction into formate. The in situ experimental observations on the reduction process and theoretical calculations reveal that the incorporation of bismuth nanoparticles with nitrogen-doped carbon matrix would promote the activation of CO2 and the easy formation of key intermediate (*OCHO), thus leading the enhanced electrocatalytic activity, with a Faradaic Efficiency (FE) of formate about 94.8 % and the long-time stability. Furthermore, the coupling of an anode for 5-hydroxymethylfurfural oxidation reaction (HMFOR) in solar-driven system renders the high 2,5-furandicarboxylic acid (FDCA) yield of 81.2 %, presenting the impressive solar-to-fuel conversion.

Constructing a Stable Built-In Electric Field in Bi/Bi2Te3 Nanowires for Electrochemical CO2 Reduction Reaction

Electrochemically converting carbon dioxide (CO2) into valuable fuels and renewable chemical feedstocks is considered a highly promising approach to achieve carbon neutrality. In this work, a robust interfacial built-in electric field (BEF) has been successfully designed and created in Bi/Bi2Te3 nanowires (NWs). The Bi/Bi2Te3 NWs consistently maintain over 90% Faradaic efficiency (FE) within a wide potential range (-0.8 to -1.2 V), with HCOOH selectivity reaching 97.2% at -1.0 V. Moreover, the FEHCOOH of Bi/Bi2Te3 NWs can still reach 94.3% at a current density of 100 mA cm-2 when it is used as a cathode electrocatalyst in a flow-cell system. Detailed in situ experiments confirm that the presence of interfacial BEF between Bi and Bi/Bi2Te3 promotes the formation of *OHCO intermediates, thus facilitating the production of HCOOH species. DFT calculations show that Bi/Bi2Te3 NWs increase the formation energies of H* and *COOH while reducing the energy barrier for *OCHO formation, thus achieving a bidirectional optimization of intermediate adsorption. This work provides a feasible scheme for exploring electrocatalytic reaction intermediates by using the BEF strategy.

Review on strategies for improving the added value and expanding the scope of CO2 electroreduction products

The electrochemical reduction of CO2 into value-added chemicals has been explored as a promising solution to realize carbon neutrality and inhibit global warming. This involves utilizing the electrochemical CO2 reduction reaction (CO2RR) to produce a variety of single-carbon (C1) and multi-carbon (C2+) products. Additionally, the electrolyte solution in the CO2RR system can be enriched with nitrogen sources (such as NO3-, NO2-, N2, or NO) to enable the synthesis of organonitrogen compounds via C-N coupling reactions. However, the electrochemical conversion of CO2 into valuable chemicals still faces challenges in terms of low product yield, poor faradaic efficiency (FE), and unclear understanding of the reaction mechanism. This review summarizes the promising strategies aimed at achieving selective production of diverse carbon-containing products, including CO, formate, hydrocarbons, alcohols, and organonitrogen compounds. These approaches involve the rational design of electrocatalysts and the construction of coupled electrocatalytic reaction systems. Moreover, this review presents the underlying reaction mechanisms, identifies the existing challenges, and highlights the prospects of the electrosynthesis processes. The aim is to offer valuable insights and guidance for future research on the electrocatalytic conversion of CO2 into carbon-containing products of enhanced value-added potential.