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.

No abstract

No abstract

For efficient electrocatalytic water-splitting, developing a nonprecious-metal-based stable and highly active material is the most challenging task. In this paper, we have devised a synthesis strategy for a hybrid catalyst composed of molybdenum carbide (Mo 2 C) and a Zr-based metal–organic framework (MOF) (UiO-66) via the solvothermal process. Synergistic effects between Mo 2 C and UiO-66 lead to a decrease in the hydrogen adsorption energy on the catalysts, and Mo 2 C/UiO-66 hybrids offer excellent catalytic activity in an alkaline environment for water-splitting. Particularly, the optimized Mo 2 C/UiO-66 hybrid, termed MCU-2 with 50:50 wt % of both components, displayed the best catalytic performance for both hydrogen and oxygen evolution reactions (HER/OER). It offered a small overpotential of 174.1 mV to attain a current density of 10 mA/cm 2 and a Tafel plot value of 147 mV/dec for HER. It also offered a low overpotential of around 180 mV to attain a current density of 20 mA/cm 2 and a Tafel plot value of 134 mV/dec for OER. Additionally, the catalyst was stable for over 24 h and ∼1000 cycles with a very minute shift in performance, and the electrolyzer indicates that a potential of ∼1.3 V is required to reach 10 mA/cm 2 current density. It can be inferred from the results that the Mo 2 C/UiO-66 hybrid is a promising candidate as a nonexpensive and active catalyst for overall electrocatalytic water-splitting as the devised catalyst exhibits enhanced kinetics for both OER and HER, a more exposed surface area, faster electron transport, and enhanced diffusion of the electrolyte.

No abstract