Ex Situ Reconstruction-Shaped Ir/CoO/Perovskite Heterojunction for Boosted Water Oxidation Reaction

Cation vacancy-induced lattice oxygen oxidation mechanism for ultra-stable OER electrocatalysis

Catalysts adhere to the adsorbate evolution mechanism (AEM) are constrained by the linear scaling relationship between the adsorbates *OOH and *OH, leading to a theoretical overpotential of approximately 370 mV. The lattice oxygen activation mechanism (LOM) is a promising strategy for developing highly active oxygen evolution reaction (OER) electrocatalysts, but it struggles to maintain the structural stability of the catalyst. Herein, transition metal oxide catalysts (MxOy-M) enriched with metal cation vacancies (VM) have been successfully built, demonstrating the OER mechanism of metal oxides changing from AEM to LOM with outstanding structural and electrocatalytic stability. Notably, the Co3O4-M catalyst maintains stable operation as long as 240 h at high current densities of 1 A cm-2 in harsh industrial condition (30 % KOH and 85 ℃). Density functional theory (DFT) calculations reveal that the downward displacement of the d-band center of the metal in MxOy-M catalysts and the upward displacement of the O 2p band center result in increased orbital overlap, thereby augmenting the covalency of the M-O bond, which effectively facilitates the LOM reaction pathway while concurrently improving the OER stability. This study has provided a universal method for regulating the transformation of the OER mechanism and facilitated the development of new efficient lattice oxygen redox OER electrocatalysts.

Amorphous-microcrystalline heterostructured high-entropy oxysulfide/cerium oxide with strong electronic communication to boost water/simulated seawater splitting

Exploring bifunctional transition metal-based oxysulfide with high activities, corrosion resistance and reaction selectivity is a promising strategy to realize efficient water/seawater splitting. Here, amorphous, high entropy and heterostructure strategies are coupled to construct the amorphous-microcrystalline heterostructured high-entropy oxysulfide/cerium oxide (a-NiCoFeOS/c-CeO2) by one-step intermittent electrodeposition. With the strong interfacial electronic communication, a-NiCoFeOS/c-CeO2 shows high bifunctional activities with low overpotentials for hydrogen evolution reaction (47/63 mV) and oxygen evolution reaction (216/220 mV) at 10 mA cm-2 in alkaline water/simulated seawater, respectively. The a-NiCoFeOS/c-CeO2 (+, -)-assembled electrolyzers require low cell voltages of 1.54/1.58 V to attain the current density of 10 mA cm-2 for overall alkaline water/simulated seawater splitting. Moreover, a-NiCoFeOS/c-CeO2 exhibits strong activity retention and high Faradaic efficiency in alkaline water/simulated seawater. Significantly, a-NiCoFeOS/c-CeO2 (+, -) tolerates the industrial alkaline water splitting condition (500 mA cm-2 in 6 M KOH @ 60 °C) with a strong durability of 210 h. Surface-reconstructed Ni/Co/Fe-based hydroxides/oxyhydroxides guarantee the high activity retention during the stability testing. The permiselective c-CeO2 and adsorbed sulfate enhance reaction selectivity and corrosion resistance by the inhibition of Cl- approach. Herein, an innovative strategy is proposed for construction of efficient water/seawater electrocatalysts, showing great potential for industrial application.

Selective A-Site Exsolution and Phase Transition in Perovskite Electrode for Efficient Flexible Znic-Air Batteries

Zinc-air batteries (ZABs) are highly promising for flexible electronics due to their high energy density and cost-effective. However, their practical application is impeded by the sluggish kinetics of the oxygen evolution and oxygen reduction reactions (OER/ORR). This study presents a novel design featuring BaO nanoparticles anchored on layered perovskite PrBaMn1.5Co0.5O6-δ (PBMC) nanofibers, fabricated through a plasma method. Notably, the plasma treatment induces the selective exsolution of A-site Ba onto the perovskite surface, while simultaneously driving the transformation of PBMC from a simple perovskite to a layered perovskite, resulting in a unique BaO/PBMC heterostructure. Theoretical calculations demonstrate that the construction of the BaO/PBMC heterojunction regulates interfacial electronic redistribution, thereby lowering energy barriers for both OER and ORR. Consequently, the BaO/PBMC air electrode exhibits superior peak power density and enhanced stability in flexible solid-state ZABs, compared to the pristine PBMC cathode. Selective A-site exsolution coupled with phase transition, featuring a unique alkaline-earth metal oxide/perovskite heterostructure, may offer new insights for energy conversion technologies.

Synthesis of IrCu/Co3O4 hybrid nanostructures and their enhanced catalytic properties toward oxygen evolution reaction under both acidic and alkaline conditions

Oxygen evolution reaction (OER) is a half-reaction that occurs at the anode during water electrolysis, and owing to its slow kinetics, it is the rate-limiting step in the process. Alloying with transition metal and combining with transition metal oxide supports are effective methods for modifying the electronic structure of noble metal catalysts and improving their catalytic properties. In this study, we synthesized IrCu/Co3O4 hybrid nanostructures by attaching IrCu alloy nanoparticles onto Co3O4 nanosheets. The electron transfer from Ir to Co altered the electronic structure of IrCu and became a crucial factor for the enhanced catalytic activity of the IrCu/Co3O4 hybrid nanostructure in the OER reaction. Additionally, the hybrid nanostructure demonstrated excellent catalytic stability under both alkaline and acidic conditions (135 and 60 h at 10 mA cm-2, respectively) due to its combination with Co3O4 nanosheets. The present work paves a new approach for the design and construction of efficient pH-universal electrocatalysts for OER.

Sulfonated reduced graphene oxide encapsulated perovskite-type ErCoFe oxide nanoparticles for efficient electrochemical water oxidation

Perovskite oxides play a vital role as electrocatalysts in water oxidation due to their flexible and unique electronic structures. In this work, Er-based perovskites ErCo1-xFexO3-δ (x = 0.0, 0.1, 0.3, 0.5, 0.7, and 1.0) denoted as EC, ECF-0.9, ECF-0.7, ECF-0.5, ECF-0.3, and EF, respectively, are synthesized by the sol-gel method. Then, ECF-0.9 is supported on sulfonated reduced graphene oxide (S-rGO) by a hydrothermal method, with weight ratios of 1 : 1 and 3 : 1 of ECF/0.9 to S-rGO (shown as ECF-0.9/S-rGO(50%) and ECF-0.9/S-rGO(75%), respectively). The structural properties and the morphology of the synthesized materials are studied using a series of different techniques. The prepared perovskites are then used as electrode materials for electrochemical water oxidation. ECF-0.9 reveals better activity than pure EF, EC, and other perovskite oxides in terms of overpotential, Tafel slope, electrochemically active surface area (ECSA), and charge transfer resistance (Rct) values. Interestingly, when the optimized perovskite oxide catalyst ECF-0.9 is decorated on S-rGO sheets, the water oxidation activity is significantly improved. ECF-0.9/S-rGO(75%) exhibits superior activity for water oxidation with an overpotential of 290 mV@10 mA cm-2 and a Tafel slope of 41 mV dec-1. Finally, overall water splitting with ECF-0.9/S-rGO(75%) as the anode electrode shows a low electrolysis voltage of 1.60 V, alongside excellent stability for 20 h.

Supersaturated Doping-Induced Maximized Metal-Support Interaction for Highly Active and Durable Oxygen Evolution

Metal-support interaction (MSI) is pivotal and ubiquitously used in the development of next-generation catalysts, offering a pathway to enhance both catalytic activity and stability. However, owing to the lattice mismatch and poor solubility, traditional catalysts often exhibit a metal-on-support heterogeneous structure with limited interfaces and interaction and, consequently, a compromised enhancement of properties. Herein, we report a universal and tunable method for supersaturated doping of transition-metal carbides via strongly nonequilibrium carbothermal shock synthesis, characterized by rapid heating and swift quenching. Our results enable ∼20 at. % Ni2FeCo doping in Mo2C, significantly surpassing the thermodynamic equilibrium limit of <3 at. %. The supersaturation ensures more catalytically active NiFeCo doping and sufficient interaction with Mo2C, resulting in the maximized MSI (Max-MSI) effect. The Max-MSI enables outstanding activity and particularly stability in alkaline oxygen evolution reaction, showing an overpotential of 284 mV at 100 mA cm-2 and stable for 700 h, while individual Ni2FeCo and Mo2C only last less than 70 and 10 h (completely dissolved), respectively. In particular, the SD-Mo2C catalyst also exhibits excellent durability at 100 mA cm-2 for up to 400 h in 7 M KOH. Such a significantly improved stability is attributed to the supersaturated doping that led to each Mo atom strongly binding with adjacent heteroatoms, thus elevating the dissolution potential and corrosion resistance of Mo2C at a high current density. Additionally, the highly dispersed NiFeCo also facilitates the formation of dense oxyhydroxide coating during reconstruction, further protecting the integrated catalysts for durable operation. Furthermore, the synthesis has been successfully scaled up to fabricate large (16 cm2) electrodes and is adaptable to nickel foam substrates, indicating promising industrial applications. Our strategy allows the general and versatile production of various highly doped transition-metal carbides, such as Ni2FeCo-doped TiC, NbC, and W2C, thus unlocking the potential of maximized or adjustable MSI for diverse catalytic applications.

ZIF-8@CsPbBr3 Nanocrystals Formed by Conversion of Pb to CsPbBr3 in Bimetallic MOFs for Enhanced Photocatalytic CO2 Reduction

Perovskite nanocrystals are embedded into metal-organic frameworks (MOFs) to create composites with high light absorption coefficients, tunable electronic properties, high specific surface area, and metal atom tunability for enhanced photocatalytic carban dioxide (CO2) reduction. However, existing perovskite-MOF structures with a large particle size are achieved based on Pb source adsorption into the pores of MOFs, which can significantly break down the porous structure, thereby resulting in a decreased specific surface area and impacting CO2 adsorption. Herein, a novel perovskite-MOF structure based on the synthesis of bimetallic Pb-containing MOFs and post-processing to convert Pb to CsPbBr3 nanocrystals (NCs) is proposed. It is discovered that the additional Pb is not introduced by adsorption, but instead engages in coordination and generates Pb-N. The produced ZIF-8@CsPbBr3 NCs are ≈40 nm and have an ultra-high specific surface area of 1325.08 m2g-1, and excellent photovoltaic characteristics, which are beneficial for photocatalytic CO2 reduction. The electronic conversion rate of composites is 450 mol g-1h-1, which is more than three times that of pure perovskites. Additionally, the superior reduction capacity is sustained after undergoing four cycles. Density Functional Thoery (DFT) simulations are used to explore the 3D charge density at the ZIF-8@CsPbBr3 NCs interface to better understand the electrical structure.

Local hydroxide ion enrichment at the inner surface of lacunaris perovskite nanotubes facilitates the oxygen evolution reaction

Numerous strategies have been devised to optimize the intrinsic activity of perovskite oxides for the oxygen evolution reaction (OER). However, conventional synthetic routes typically yield limited numbers of active sites and low mass activities. More critically, the sluggish mass transfer poses a huge challenge, particularly under high polarization conditions, which impedes the overall reaction kinetics. Herein, lacunaris La0.5Pr0.25Ba0.25Co0.8Ni0.2O3-δ nanotubes (LPBCN-NTs) were prepared via electrospinning and post-annealing, which exhibited a small overpotential of 358.8 mV at 10 mA cm-2 and a lower Tafel slope of 71.46 mV dec-1, superior to the values for the same stoichiometric LPBCN nanoparticles and solid nanofibers, state-of-the-art counterparts and commercial IrO2. Density functional theory calculations revealed that the surface oxygen vacancies in LPBCN-NTs significantly lowered the OH- adsorption energy, while finite element analysis indicated that the precisely constructed lacunaris NT structure enriched the OH- concentration at its inner surface by an order of magnitude, both of which collectively resulted in accelerated OER kinetics. This study clarifies the underlying mechanism of how the lacunaris nanotubular architecture and the surface oxygen vacancies of perovskite oxides affect heterocatalysis, which undoubtedly paves the way to handling the long-standing issues of sluggish mass transfer rates and poor intrinsic catalytic activity.

In situ investigation of ruthenium doped lanthanum nickel titanium double perovskite and its exsolution behaviour

Exsolution, an innovative method for fabricating perovskite-based oxides decorated with metal nanoparticles, has garnered significant interest in the fields of catalyst fabrication and electrochemical devices. Although dopant exsolution from single perovskite structures has been extensively studied, the exsolution behaviour of double perovskite structures remains insufficiently understood. In this study, we synthesized B-site double perovskite Ru-doped lanthanum nickel titanates with a 7.5 at% A-site deficiency, and systematically investigated the exsolution process that formed nickel metal nanoparticles on the material surface, across a broad reduction temperature range of 350-1000 °C. Both Ex situ and in situ characterization revealed that small, uniform Ni nanoparticles exsolved at low temperatures, whereas the exsolution of ruthenium required higher reduction temperatures beyond 1000 °C. Within the reduction temperature range of 350-500 °C, a notable finding is the reconstruction of exsolved nanoparticles, implying that Ni particles exist in a thermodynamically metastable state. Electrochemical impedance spectroscopy (EIS) showed a decreased area specific resistance (ASR) during the progress of exsolution. The increase in current density of a full solid oxide cell (SOC) in electrolysis mode and the doubling of peak power density in fuel cell mode attributed to the exsolution of Ni nanoparticles highlight the potential application of metal exsolution in electrode materials for SOCs.

Rapid Construction of Double Crystalline Prussian Blue Analogue Hetero-Superstructure

The controllable construction of complex metal-organic coordination polymers (CPs) merits untold scientific and technological potential, yet remains a grand challenge of one-step construction and modulating simultaneously valence states of metals and topological morphology. Here, a thiocyanuric acid (TCA)-triggered strategy is presented to one-step rapid synthesis a double-crystalline Prussian blue analogue hetero-superstructure (PBA-hs) that comprises a Co3[Fe(CN)6]2 cube overcoated with a KCo[Fe(CN)6] shell, followed by eight self-assembled small cubes on vertices. Unlike common directing surfactants, TCA not only acts as a trigger for the fast growth of KCo[Fe(CN)6] on the Co3[Fe(CN)6]2 phase resulting in a PBA-on-PBA hetero-superstructure, but also serves as a flange-like bridge between them. By combining experiments with simulations, a deprotonation-induced electron transfer (DIET) mechanism is proposed for formation of second phase in PBA-hs, differing from thermally and photo-induced electron transfer processes. To prove utility, the calcined PBA-hs exhibits enhanced oxygen evolution reaction performance. This work provides a new method to design of novel CPs for enriching chemistry and material science. This work offers a practical approach to design novel CPs for enriching chemistry and material science.

Effect of Ni Sulfate Residue on Oxygen Evolution Reaction (OER) in Porous NiFe@NiFe Layered Double Hydroxide

The development of cost-effective and high-performance oxygen evolution reaction (OER) catalysts is a significant challenge. This study presents the synthesis of binder-free NiFe@NiFe layered double hydroxide (NNF) via one-pot electrodeposition on carbon paper and Ni foam at high current densities. The presence of Ni sulfate residues on the prepared NNF is also investigated. The findings indicate that Ni sulfate significantly improves OER performance and durability. The sulfate content can be controlled by varying the method and duration of washing. NNF prepared through dipping (NNF-D) exhibits outstanding OER activity with a low overpotential of 241 mV, which is 25 mV lower than that of NNF washed for 60 s (NNF-W-60 s) at 10 mA cm-2 in 1 m KOH. Furthermore, density functional theory analyses indicate that the Ni sulfate residue helps modify the electronic structure, thereby optimizing the binding strength of *OOH. This synthetic strategy is expected to inspire the development of next-generation catalysts utilizing various adsorbates.

Transfer learning guided discovery of efficient perovskite oxide for alkaline water oxidation

Perovskite oxides show promise for the oxygen evolution reaction. However, numerical chemical compositions remain unexplored due to inefficient trial-and-error methods for material discovery. Here, we develop a transfer learning paradigm incorporating a pre-trained model, ensemble learning, and active learning, enabling the prediction of undiscovered perovskite oxides with enhanced generalizability for this reaction. Screening 16,050 compositions leads to the identification and synthesis of 36 new perovskite oxides, including 13 pure perovskite structures. Pr0.1Sr0.9Co0.5Fe0.5O3 and Pr0.1Sr0.9Co0.5Fe0.3Mn0.2O3 exhibit low overpotentials of 327 mV and 315 mV at 10 mA cm-2, respectively. Electrochemical measurements reveal coexistence of absorbate evolution and lattice oxygen mechanisms for O-O coupling in both materials. Pr0.1Sr0.9Co0.5Fe0.3Mn0.2O3 demonstrates enhanced OH- affinity compared to Pr0.1Sr0.9Co0.5Fe0.5O3, with the emergence of oxo-bridged Mn-Co conjugate facilitating charge redistribution and dynamic reversibility of Olattice/VO, thereby slowing down Co dissolution. This work paves the way for accelerated discovery and development of high-performance perovskite oxide electrocatalysts for this reaction.

Laser-Induced Controllable Porosity in Additive Manufacturing Boosts Efficiency of Electrocatalytic Water Splitting

In laser-based additive manufacturing (AM), porosity and unmelted metal powder are typically considered undesirable and harmful. Nevertheless in this work, precisely controlling laser parameters during printing can intentionally introduce controllable porosity, yielding a porous electrode with enhanced catalytic activity for the oxygen evolution reaction (OER). This study demonstrates that deliberate introduction of porosity, typically considered a defect, leads to improved gas molecule desorption, enhanced mass transfer, and increased catalytically active sites. The optimized P-93% electrode displays superior OER performance with an overpotential of 270 mV at 20 mA cm-2. Furthermore, it exhibits remarkable long-term stability, operating continuously for over 1000 h at 10 mA cm-2 and more than 500 h at 500 mA cm-2. This study not only provides a straightforward and mass-producible method for efficient, binder-free OER catalysts but also, if optimized, underscores the potential of laser-based AM driven defect engineering as a promising strategy for industrial water splitting.

Recent development and applications of differential electrochemical mass spectrometry in emerging energy conversion and storage solutions

Electrochemical energy conversion and storage are playing an increasingly important role in shaping the sustainable future. Differential electrochemical mass spectrometry (DEMS) offers an operando and cost-effective tool to monitor the evolution of gaseous/volatile intermediates and products during these processes. It can deliver potential-, time-, mass- and space-resolved signals which facilitate the understanding of reaction kinetics. In this review, we show the latest developments and applications of DEMS in various energy-related electrochemical reactions from three distinct perspectives. (I) What is DEMS addresses the working principles and key components of DEMS, highlighting the new and distinct instrumental configurations for different applications. (II) How to use DEMS tackles practical matters including the electrochemical test protocols, quantification of both potential and mass signals, and error analysis. (III) Where to apply DEMS is the focus of this review, dealing with concrete examples and unique values of DEMS studies in both energy conversion applications (CO2 reduction, water electrolysis, carbon corrosion, N-related catalysis, electrosynthesis, fuel cells, photo-electrocatalysis and beyond) and energy storage applications (Li-ion batteries and beyond, metal-air batteries, supercapacitors and flow batteries). The recent development of DEMS-hyphenated techniques and the outlook of the DEMS technique are discussed at the end. As DEMS celebrates its 40th anniversary in 2024, we hope this review can offer electrochemistry researchers a comprehensive understanding of the latest developments of DEMS and will inspire them to tackle emerging scientific questions using DEMS.

Crystalline-Amorphous Interfaces Engineering of CoO-InOx for Highly Efficient CO2 Electroreduction to CO

As a fundamental product of CO2 conversion through two-electron transfer, CO is used to produce numerous chemicals and fuels with high efficiency, which has broad application prospects. In this work, it has successfully optimized catalytic activity by fabricating an electrocatalyst featuring crystalline-amorphous CoO-InOx interfaces, thereby significantly expediting CO production. The 1.21%CoO-InOx consists of randomly dispersed CoO crystalline particles among amorphous InOx nanoribbons. In contrast to the same-phase structure, the unique CoO-InOx heterostructure provides plentiful reactive crystalline-amorphous interfacial sites. The Faradaic efficiency of CO (FECO) can reach up to 95.67% with a current density of 61.72 mA cm-2 in a typical H-cell using MeCN containing 0.5 M 1-Butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) as the electrolyte. Comprehensive experiments indicate that CoO-InOx interfaces with optimization of charge transfer enhance the double-layer capacitance and CO2 adsorption capacity. Theoretical calculations further reveal that the regulating of the electronic structure at interfacial sites not only optimizes the Gibbs free energy of *COOH intermediate formation but also inhibits HER, resulting in high selectivity toward CO.

Partial Exsolution Enables Superior Bifunctionality of Ir@SrIrO3 for Acidic Overall Water Splitting

The pursuit of efficient and durable bifunctional electrocatalysts for overall water splitting in acidic media is highly desirable, albeit challenging. SrIrO3 based perovskites are electrochemically active for oxygen evolution reaction (OER), however, their inert activities toward hydrogen evolution reaction (HER) severely restrict the practical implementation in overall water splitting. Herein, an Ir@SrIrO3 heterojunction is newly developed by a partial exsolution approach, ensuring strong metal-support interaction for OER and HER. Notably, the Ir@SrIrO3-175 electrocatalyst, prepared by annealing SrIrO3 in 5% H2 atmosphere at 175 °C, delivers ultralow overpotentials of 229 mV at 10 mA cm-2 for OER and 28 mV at 10 mA cm-2 for HER, surpassing most recently reported bifunctional electrocatalysts. Moreover, the water electrolyzer using the Ir@SrIrO3-175 bifunctional electrocatalyst demonstrates the potential application prospect with high electrochemical performance and excellent durability in acidic environment. Theoretical calculations unveil that constructing Ir@SrIrO3 heterojunction regulates interfacial electronic redistribution, ultimately enabling low energy barriers for both OER and HER.

A Doping-Induced SrCo0.4Fe0.6O3/CoFe2O4 Nanocomposite for Efficient Oxygen Evolution in Alkaline Media

Perovskite and spinel oxides are promising alternatives to noble metal-based electrocatalysts for oxygen evolution reaction (OER). Herein, a novel perovskite/spinel nanocomposite comprised of SrCo0.4Fe0.6O3 and CoFe2O4 (SCF/CF) is prepared through a simple one-step method that incorporates iron doping into a SrCoO3- δ matrix, circumventing complex fabrication processes typical of these materials. At a Fe dopant content of 60%, the CoFe2O4 spinel phase is directly precipitated from the parent SrCo0.4Fe0.6O3 perovskite phase and the number of active B-site metals (Co/Fe) in the parent SCF can be maximized. This nanocomposite exhibits a remarkable OER activity in alkaline media with a small overpotentional of 294 mV at 10 mA cm-2. According to surface states analysis, the parent SCF perovskite remains in its pristine form under alkaline OER conditions, serving as a stable substrate, while the second spinel CF is covered by 5/8 monolayer (ML) O*, exhibiting considerable affinity toward the oxygen species involved in the OER. Analysis based on advanced OER microkinetic volcano model indicates that a 5/8 ML O* covered-CF is the origin for the remarkable activity of this nanocomposite. The results reported here significantly advance knowledge in OER and can boost application, scale-up and commercialisation of electrocatalytic technologies toward clean energy devices.

Bifunctional Electrocatalysts for Overall and Hybrid Water Splitting

Electrocatalytic water splitting driven by renewable electricity has been recognized as a promising approach for green hydrogen production. Different from conventional strategies in developing electrocatalysts for the two half-reactions of water splitting (e.g., the hydrogen and oxygen evolution reactions, HER and OER) separately, there has been a growing interest in designing and developing bifunctional electrocatalysts, which are able to catalyze both the HER and OER. In addition, considering the high overpotentials required for OER while limited value of the produced oxygen, there is another rapidly growing interest in exploring alternative oxidation reactions to replace OER for hybrid water splitting toward energy-efficient hydrogen generation. This Review begins with an introduction on the fundamental aspects of water splitting, followed by a thorough discussion on various physicochemical characterization techniques that are frequently employed in probing the active sites, with an emphasis on the reconstruction of bifunctional electrocatalysts during redox electrolysis. The design, synthesis, and performance of diverse bifunctional electrocatalysts based on noble metals, nonprecious metals, and metal-free nanocarbons, for overall water splitting in acidic and alkaline electrolytes, are thoroughly summarized and compared. Next, their application toward hybrid water splitting is also presented, wherein the alternative anodic reactions include sacrificing agents oxidation, pollutants oxidative degradation, and organics oxidative upgrading. Finally, a concise statement on the current challenges and future opportunities of bifunctional electrocatalysts for both overall and hybrid water splitting is presented in the hope of guiding future endeavors in the quest for energy-efficient and sustainable green hydrogen production.

Interface Charge Distribution Engineering of Pd-CeO2 /C for Efficient Carbohydrazide Oxidation Reaction

Carbohydrazide electrooxidation reaction (COR) is a potential alternative to oxygen evolution reaction in water splitting process. However, the sluggish kinetics process impels to develop efficient catalysts with the aim of the widespread use of such catalytic system. Since COR concerns the adsorption/desorption of reactive species on catalysts, the electronic structure of electrocatalyst can affect the catalytic activity. Interface charge distribution engineering can be considered to be an efficient strategy for improving catalytic performance, which facilitates the cleavage of chemical bond. Herein, highly dispersed Pd nanoparticles on CeO2 /C catalyst are prepared and the COR catalytic performance is investigated. The self-driven charge transfer between Pd and CeO2 can form the local nucleophilic and electrophilic region, promoting to the adsorption of electron-withdrawing and electron-donating group in carbohydrazide molecule, which facilitates the cleavage of C-N bond and the carbohydrazide oxidation. Due to the local charge distribution, the Pd-CeO2 /C exhibits superior COR catalytic activity with a potential of 0.27 V to attain 10 mA cm-2 . When this catalyst is used for energy-efficient electrolytic hydrogen production, the carbohydrazide electrolysis configuration exhibits a low cell voltage (0.6 V at 10 mA cm-2 ). This interface charge distribution engineering can provide a novel strategy for improving COR catalytic activity.

A layered CoSeO3 pre-catalyst for electrocatalytic water oxidation

In electrocatalytic water oxidation, the surface reconstruction of electrocatalysts is a common issue due to the applied anodic potential. The study of the fundamentals of catalyst structure transformation and the relationship between structure and performance is important. Herein, we designed two cobalt selenites (CoSeO3 and CoSeO3·2H2O) with different structures for comparative studies. The cross channels in layered CoSeO3 provide space for easy surface reconstruction. The reasons are defined by a series of electrochemical studies, indicating a larger ion diffusion coefficient, more surface contacting OH- anions and faster charge transfer kinetics in CoSeO3. This work provided a paradigm for studying the influence of geometric structure on pre-catalyst reconstruction.