Summary A significant interest in the exploration of clean and renewable alternative energy resources has been observed in recent years to combat environmental pollution and energy shortages for a sustainable future. In this regard, hydrogen is clean, energy‐rich fuel with unlimited potential. It can be produced via water‐splitting process using the most abundant resources on earth, that is, water and solar/electrical energy. Metal‐organic frameworks (MOFs) are a category of porous crystalline materials with well‐organized structures and unique catalytic, optical, and electrical properties. MOFs and MOF‐derived materials have proved to be excellent catalysts for water‐splitting both by electrochemical and photoelectrochemical (PEC) routes. Furthermore, photochemical and electrochemical capabilities of these MOFs can be fine‐tuned to maximize their performance by modification in the bandgap, surface area, current density, electrochemical active surface area, and overpotential, through tailoring of the organic ligands and/or metal centers. A number of works have been dedicated to this quest resulting in promising and very effective results. Such as for photoelectrocatalysis, a composite nanorod array of TiO2/Co‐MOF acting as photoanode achieved one of the highest photocurrent densities of 2.93 mA/cm2 at 1.23 V (vs reverse hydrogen electrode [RHE]). In another study, MOF‐derived Co3C‐3/TiO2 photoanode attained the photocurrent density of 2.6 mA/cm2 at 1.23 V vs RHE. For electrocatalysis, Fe2O3/Ni‐MOF‐74 exhibited oxygen evolution reaction overpotential of 264 mV to reach 10 mA/cm2 of current density with a low Tafel plot of 48 mV/dec. Another novel material derived from MOF, MoO2‐PC‐rGO displayed a Tafel Plot of 41 mV/dec. Even though this field is in its infancy phase, it is attracting increased attention for promising results suggesting extraordinary potential for practical applications. Focus of this review article is on the overview of the development of MOFs for application in electrocatalytic and photoelectrocatalytic water‐splitting for hydrogen production. This review intends to provide a timely reference and insight for the advancement in catalysts based on MOFs for practical electrochemical and PEC water‐splitting in a clear and comprehensive manner. Starting with the brief introduction, fundamentals, factors affecting catalytic efficiency and evaluation parameters of water‐splitting are summarized followed by synthesis strategies and recent progress made by MOF‐based catalysts for PEC and electrochemical water‐splitting.

Electrocatalysis is an efficient and promising means of energy conversion, with minimal environmental footprint. To enhance reaction rates, catalysts are required to minimize overpotential. Alternatives to noble metal electrocatalysts are essential to address these needs on a large scale. In this context, transition metal nitride (TMN) nanoparticles have attracted much attention owing to their high catalytic activity, distinctive electronic structures, and enhanced surface morphologies. Nickel‐based materials are an ideal choice for electrocatalysts given nickel's abundance and low cost in comparison to noble metals. In this Minireview, advancements made specifically in Ni‐based binary and ternary TMNs as electrocatalysts for the oxygen evolution reaction (OER) are critically evaluated. When used as OER electrocatalysts, Ni‐based nanomaterials with 3 D architectures on a suitable support (e.g., a foam support) speed up electron transfer as a result of well‐oriented crystal structures and also assist intermediate diffusion, during reaction, of evolved gases. 2 D Ni‐based nitride sheet materials synthesized without supports usually perform better than 3 D supported electrocatalysts. The focus of this Minireview is a systematic description of OER activity for state‐of‐the‐art Ni‐based nitrides as nanostructured electrocatalysts.

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