Common Pitfalls of Reporting Electrocatalysts for Water Splitting

Harnessing the Synergistic Effects of Ir Co-Decorated NiMn-LDH: a Multi-Analytical Approach to Boost Electrocatalytic Overall Water Splitting Activity in Alkaline Condition

Fine control over the Ir precursor to the Nickel-based layered double hydroxides (LDHs) is significant for decorating both single atoms (SA) and nanoclusters (NC), thus modulating catalytic kinetics and improving overall performance. In this study, NiMn-LDH is synthesized and co-decorated it with Iridium, introducing a new pathway for developing efficient bifunctional electrocatalysts in water-splitting technologies. Additionally, a typical fibrous material has developed by immobilizing.I r SA - I r N C 12 - NiMn - LDH ${\mathrm{I}}{{{\mathrm{r}}}^{{\mathrm{SA}}}} - {\mathrm{I}}{{{\mathrm{r}}}^{{\mathrm{N}}{{{\mathrm{C}}}_{12}}}} - {\mathrm{NiMn}} - {\mathrm{LDH}}$ onto PAN (polyacrylonitrile) nanofibers (I r SA - I r N C 12 - NiMn - LDH - F ${\mathrm{I}}{{{\mathrm{r}}}^{{\mathrm{SA}}}} - {\mathrm{I}}{{{\mathrm{r}}}^{{\mathrm{N}}{{{\mathrm{C}}}_{12}}}} - {\mathrm{NiMn}} - {\mathrm{LDH}} - {\mathrm{F}}$ ) using a feasible electrospinning technique. Notably, the catalyst exhibits low overpotentials of 249 and 110 mV for oxygen (OER) and hydrogen evolution reactions (HER) at 10 mA cm- 2, and a low cell voltage of 1.65 V for total water splitting (TWS). Additionally,I r SA - I r N C 12 - NiMn - LDH - F ${\mathrm{I}}{{{\mathrm{r}}}^{{\mathrm{SA}}}} - {\mathrm{I}}{{{\mathrm{r}}}^{{\mathrm{N}}{{{\mathrm{C}}}_{12}}}} - {\mathrm{NiMn}} - {\mathrm{LDH}} - {\mathrm{F}}$ remained stable and effective in alkaline OER, HER, and TWS for over 50 h. Furthermore, X-ray adsorption near-edge spectrum (XANES) experiments, together with theoretical calculations, show that the synergistic effect of IrSA andI r N C 12 ${\mathrm{I}}{{{\mathrm{r}}}^{{\mathrm{N}}{{{\mathrm{C}}}_{12}}}}$ which helps to enhance the catalytic activity, promoting electron rearrangement and lowering the reaction energy barrier.

High Catalytic Selectivity of Electron/Proton Dual-Conductive Sulfonated Polyaniline Micropore Encased IrO2 Electrocatalyst by Screening Effect for Oxygen Evolution of Seawater Electrolysis

Acidic seawater electrolysis offers significant advantages in high efficiency and sustainable hydrogen production. However, in situ electrolysis of acidic seawater remains a challenge. Herein, a stable and efficient catalyst (SPTTPAB/IrO2) is developed by coating iridium oxide (IrO2) with a microporous conjugated organic framework functionalized with sulfonate groups (-SO3H) to tackle these challenges. The SPTTPAB/IrO2 presents a -SO3H concentration of 5.62 × 10-4 mol g-1 and micropore below 2 nm numbering 1.026 × 1016 g-1. Molecular dynamics simulations demonstrate that the conjugated organic framework blocked 98.62% of Cl- in seawater from reaching the catalyst. This structure combines electron conductivity from the organic framework and proton conductivity from -SO3H, weakens the Cl- adsorption, and suppresses metal-chlorine coupling, thus enhancing the catalytic activity and selectivity. As a result, the overpotential for the oxygen evolution reaction (OER) is only 283 mV@10 mA cm-2, with a Tafel slope of 16.33 mV dec-1, which reduces 13.8% and 37.8% compared to commercial IrO2, respectively. Impressively, SPTTPAB/IrO2 exhibits outstanding seawater electrolysis performance, with a 35.3% improvement over IrO2 to 69 mA cm-2@1.9 V, while the degradation rate (0.018 mA h-1) is only 24.6% of IrO2. This study offers an innovative solution for designing high-performance seawater electrolysis electrocatalysts.

Transition metal-based electrocatalysts for alkaline overall water splitting: advancements, challenges, and perspectives

Water electrolysis is a promising method for efficiently producing hydrogen and oxygen, crucial for renewable energy conversion and fuel cell technologies. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are two key electrocatalytic reactions occurring during water splitting, necessitating the development of active, stable, and low-cost electrocatalysts. Transition metal (TM)-based electrocatalysts, spanning noble metals and TM oxides, phosphides, nitrides, carbides, borides, chalcogenides, and dichalcogenides, have garnered significant attention due to their outstanding characteristics, including high electronic conductivity, tunable valence electron configuration, high stability, and cost-effectiveness. This timely review discusses developments in TM-based electrocatalysts for the HER and OER in alkaline media in the last 10 years, revealing that the exposure of more accessible surface-active sites, specific electronic effects, and string effects are essential for the development of efficient electrocatalysts towards electrochemical water splitting application. This comprehensive review serves as a guide for designing and constructing state-of-the-art, high-performance bifunctional electrocatalysts based on TMs, particularly for applications in water splitting.

Advancing Catalysts by Stacking Fault Defects for Enhanced Hydrogen Production: A Review

Green hydrogen, derived from water splitting powered by renewable energy such as solar and wind energy, provides a zero-emission solution crucial for revolutionizing hydrogen production and decarbonizing industries. Catalysts, particularly those utilizing defect engineering involving the strategical introduction of atomic-level imperfections, play a vital role in reducing energy requirements and enabling a more sustainable transition toward a hydrogen-based economy. Stacking fault (SF) defects play an important role in enhancing the electrocatalytic processes by reshaping surface reactivity, increasing active sites, improving reactants/product diffusion, and regulating electronic structure due to their dense generation ability and profound impact on catalyst properties. This review explores SF in metal-based materials, covering synthetic methods for the intentional introduction of SF and their applications in hydrogen production, including oxygen evolution reaction, photo- and electrocatalytic hydrogen evolution reaction, overall water splitting, and various other electrocatalytic processes such as oxygen reduction reaction, nitrate reduction reaction, and carbon dioxide reduction reaction. Finally, this review addresses the challenges associated with SF-based catalysts, emphasizing the importance of a detailed understanding of the properties of SF-based catalysts to optimize their electrocatalytic performance. It provides a comprehensive overview of their various applications in electrocatalytic processes, providing valuable insights for advancing sustainable energy technologies.

Recent Progress on Nickel- and Iron-Based Metallic Organic Frameworks for Oxygen Evolution Reaction: A Review

Developing sustainable energy solutions to safeguard the environment is a critical ongoing demand. Electrochemical water splitting (EWS) is a green approach to create effective and long-lasting electrocatalysts for the water oxidation process. Metal organic frameworks (MOFs) have become commonly utilized materials in recent years because of their distinguishing pore architectures, metal nodes easy accessibility, large specific surface areas, shape, and adaptable function. This review outlines the most significant developments in current work on developing improved MOFs for enhancing EWS. The benefits and drawbacks of MOFs are first discussed in this review. Then, some cutting-edge methods for successfully modifying MOFs are also highlighted. Recent progress on nickel (Ni) and iron (Fe) based MOFs have been critically discussed. Finally, a comprehensive analysis of the existing challenges and prospects for Ni- and Fe-based MOFs are summarized.

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Constructed Interfacial Oxygen-Bridge Chemical Bonding in Core-Shell Transition Metal Phosphides/Carbon Hybrid Boosting Oxygen Evolution Reaction

A designed structure which CoP nanoparticles (NPs) ingeniously connected with graphene-like carbon layer via in-situ generated interfacial oxygen-bridge chemical bonding was achieved by a mild phosphorization treatment. The results proved that the presence of phosphorus vacancies is a crucial factor enabling formation of Co-O-C bonds. The direct coupling of edge Co of CoP with the oxygen from functional groups on the carbon layer was proposed. As a catalyst for electrocatalytic water splitting, the manufactured Fe₂ O₃ @C@CoP core-shell structure manifested a low overpotential of 230 mV, a low Tafel slope of 55 mV dec^-1 , and long-term stability. Density functional theory calculations verified that the Co-O-C bond played a critical role in decreasing the thermodynamic energy barrier of reaction rate-determining step for the oxygen evolution reaction (OER). This synthetic route might be extended to construct metal-O-C bonds in other transition metal phosphides (or selenides, sulfides)/carbon composites for highly efficient OER catalysts.