Nanostructured core-shell cobalt chalcogenides for efficient water oxidation in alkaline electrolyte

Review of Catalytic Electrodes Containing Iron-Cobalt-Nickel Composite Components for Water Electrolysis

Transition metal-based electrocatalytic materials for hydrogen production through water splitting offer advantages in terms of price and availability compared to noble metal-based catalysts, among which, Fe-, Co-, and Ni-based compounds are the most typical and widely studied materials. Utilizing the synergistic effects between composite components in compounds containing multiple metal elements is an important way to improve the catalytic performance of catalysts, so developing ternary or multiple active center catalysts containing Fe, Co, and Ni is a promising direction. In this mini-review, we provide an summary of the latest achievements of water splitting catalyst materials simultaneously containing Fe, Co, and Ni elements. It was summarized according to several groups including compounds of boron-/carbon-/nitrogen-/phosphorus-/oxygen-group elements, metal-organic framework-based compounds, and compounds in situ grown from alloy matrix. Also challenges that need to be addressed are presented at the end of the article.

Facile synthesis of Co3Te4-Fe3C for efficient overall water-splitting in an alkaline medium

The large amounts of attention directed towards the commercialization of renewable energy systems have motivated extensive research to develop non-precious-metal-based catalysts for promoting the electrochemical production of H2 and O2 from water. Here, we report promising technology, i.e., electrochemical water splitting for OER and HER. This work used a simple hydrothermal method to synthesize a novel Co3Te4-Fe3C nanocomposite directly on a stainless-steel substrate. Various physical techniques like XRD, FESEM/EDX, and XPS have been used to characterize the good composite growth and confirm the correlation between the structural features. It has been shown that the composite's morphology consists of interconnected particles, each uniformly coated with a thin layer of carbon. This structure then forms a porous network with defects, which helps stabilize the material and improve its charge conductivity. XPS analysis shows that combining Fe3C with Co3Te4 adjusts the atomic structure of both metals. This interaction creates redox sites (Fe3+/Fe2+ and Co3+/Co2+) at the Co₃Te₄-Fe₃C interface, which are crucial for activating redox reactions and enhancing electrochemical performance. The results also confirm the presence of multiple synergistic active sites, which contribute to improved catalytic activity. The optimized chemical composition and conductive structure result in enhanced electrocatalytic activity of Co3Te4-Fe3C towards electron transportation between the material interface and medium. It is found that the Co3Te4-Fe3C catalyst exhibits robust OER/HER activity with reduced overpotential values of 235/210 mV@10 mA cm-2 and Tafel slopes of 62/45 mV dec-1 in an alkaline solution. For overall water-splitting, cell voltages of 1.44, 1.88, and 2.0 V at current densities of 10, 50, and 100 mA cm-2 were achieved with a stability of 102 h. The electrochemically active surface area of the composite is 1125 cm2, indicating that a large surface area offered numerous reactive sites for electron transfer in the promotion of the electrochemical activity. The enhancement in catalytic performance was also checked using chronoamperometry analysis, reflecting long-term stability. Our results provide a novel idea for designing a composite of carbide with chalcogenide with robust catalytic mechanisms, which is useful for various applications in environmental and energy conversion fields.

A Review of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) have emerged as a class of materials for the oxygen evolution reaction (OER). Because of their high earth abundance, electrical conductivity, and OER performance, these electrocatalysts have the potential to enable the practical application of green energy conversion and storage. Under OER potentials, X-ide electrocatalysts demonstrate various degrees of oxidation resistance due to their differences in chemical composition, crystal structure, and morphology. Depending on their resistance to oxidation, these catalysts will fall into one of three post-OER electrocatalyst categories: fully oxidized oxide/(oxy)hydroxide material, partially oxidized core@shell structure, and unoxidized material. In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Previous review papers have provided limited conclusions and have omitted the significance of "catalytically active sites/species/phases" in X-ide OER electrocatalysts. In this review, a comprehensive summary of (i) experimental parameters (e.g., substrates, electrocatalyst loading amounts, geometric overpotentials, Tafel slopes, etc.) and (ii) electrochemical stability tests and post-analyses in X-ide OER electrocatalyst publications from 2013 to 2022 is provided. Both mono and polyanion X-ides are discussed and classified with respect to their material transformation during the OER. Special analytical techniques employed to study X-ide reconstruction are also evaluated. Additionally, future challenges and questions yet to be answered are provided in each section. This review aims to provide researchers with a toolkit to approach X-ide OER electrocatalyst research and to showcase necessary avenues for future investigation.

Recent Advances in Transition Metal Tellurides (TMTs) and Phosphides (TMPs) for Hydrogen Evolution Electrocatalysis

The hydrogen evolution reaction (HER) is a developing and promising technology to deliver clean energy using renewable sources. Presently, electrocatalytic water (H₂O) splitting is one of the low-cost, affordable, and reliable industrial-scale effective hydrogen (H₂) production methods. Nevertheless, the most active platinum (Pt) metal-based catalysts for the HER are subject to high cost and substandard stability. Therefore, a highly efficient, low-cost, and stable HER electrocatalyst is urgently desired to substitute Pt-based catalysts. Due to their low cost, outstanding stability, low overpotential, strong electronic interactions, excellent conductivity, more active sites, and abundance, transition metal tellurides (TMTs) and transition metal phosphides (TMPs) have emerged as promising electrocatalysts. This brief review focuses on the progress made over the past decade in the use of TMTs and TMPs for efficient green hydrogen production. Combining experimental and theoretical results, a detailed summary of their development is described. This review article aspires to provide the state-of-the-art guidelines and strategies for the design and development of new highly performing electrocatalysts for the upcoming energy conversion and storage electrochemical technologies.

Carbon-Based Composites as Electrocatalysts for Oxygen Evolution Reaction in Alkaline Media

This review paper presents the most recent research progress on carbon-based composite electrocatalysts for the oxygen evolution reaction (OER), which are of interest for application in low temperature water electrolyzers for hydrogen production. The reviewed materials are primarily investigated as active and stable replacements aimed at lowering the cost of the metal electrocatalysts in liquid alkaline electrolyzers as well as potential electrocatalysts for an emerging technology like alkaline exchange membrane (AEM) electrolyzers. Low temperature electrolyzer technologies are first briefly introduced and the challenges thereof are presented. The non-carbon electrocatalysts are briefly overviewed, with an emphasis on the modes of action of different active phases. The main part of the review focuses on the role of carbon–metal compound active phase interfaces with an emphasis on the synergistic and additive effects. The procedures of carbon oxidative pretreatment and an overview of metal-free carbon catalysts for OER are presented. Then, the successful synthesis protocols of composite materials are presented with a discussion on the specific catalytic activity of carbon composites with metal hydroxides/oxyhydroxides/oxides, chalcogenides, nitrides and phosphides. Finally, a summary and outlook on carbon-based composites for low temperature water electrolysis are presented.

Solvent dispersion triggered the formation of NiFe-gel as an efficient electrocatalyst for enhancing the oxygen evolution reaction

The inexpensive metal-based electrocatalysts with large surface areas are in high demand to overcome the sluggish kinetics of the anodic oxygen evolution reaction (OER) in electrocatalytic water splitting. Here we report that a series of NiFe based gels were prepared by a solvent dispersion triggered gelation method, where Ni2Fe-gel exhibits a specific surface area of 216.9 m2 g-1, and a low overpotential of 245 mV at 10 mA cm-2 in an alkaline electrolyte.

Surface vacancy on PtTe2 for promoting CO oxidation through efficiently activating O2

Platinum group metal dichalcogenides (PtTe₂) with controllable thickness have been synthesized and confirmed to be promising electric and spintronic materials. Here, using the first-principles calculations, we demonstrate the potential application of PtTe₂ as catalyst substrate. Taking CO oxidation as model reaction, the importance of surface vacancy is clarified. It is found that surface vacancy on PtTe₂ could improve the stability and catalytic activity of the supported Pt atom. The details of CO oxidation processes indicate that surface vacancy could weaken the adsorption of reactants and speed up the formation and decomposition of OOCO intermediate on Pt catalysts. The underlying mechanisms for the improved activity are unveiled through comprehensively analyzing the charge transfer, density of states, and charge density difference. We hope that the current findings were beneficial for the research and development of efficient catalysts by collocating various single atom/cluster catalysts with different platinum group metal dichalcogenides.