Recent Advances in Non‐Precious Metal‐Based Electrodes for Alkaline Water Electrolysis

Abstract

Hydrogen gas has been regarded as an ideal energy source that could replace the need of fossil fuels, based on its high energy density with zero carbon emissions. The production of hydrogen via electrolysis of water is not a new field, but the technology has seen significant advancements in recent times, owing to the proportional growing demand of clean and affordable energy. This review discusses the most recent progresses achieved in the area of earth abundant catalysis, particularly, non‐precious metal (Ni, Co, Fe, Mo, W)‐based catalysts that are being utilized for the electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solutions. Based on the type of materials, the discussions are categorized into sections attributed to transition metal alloys, hydroxides, oxides, chalcogenides, carbides and nitrogenous materials. In general, a brief introduction of HER and OER mechanisms followed by a detailed discussion of the presently considered catalysts with endeavors have been made to highlight the new technologies and alternative approaches that are being considered promising towards production of clean H2 energy. Finally, a prospective has been provided to accentuate the future of non‐noble metal based catalyst in electro‐catalytic water splitting reactions.

Main Hydrogen Production Processes: An Overview

“…In alkaline electrolysis cell, the electrodes are immersed in the liquid electrolyte, typically a 25-30 wt% solution of KOH or NaOH separated by a diaphragm. Anodic (12) and cathodic reactions (13) The choice of the electrocatalysts is a critical issue, those based on noble metals are highly efficient, on the other hand, the most convenient material used for the electrodes are Ni-based [158,159], however to improve the performance and reduce the degradation, a series of metals can be used as additives, including cobalt, vanadium iron and selenide [160]. The use of noble metal-based electrodes could provide better performance however, cheaper alternative would be preferred.…”

Recent Progress on Structurally Ordered Materials for Electrocatalysis

“…On the other hand, non‐precious‐metal electrocatalysts such as alloys, oxides, (oxy)hydroxides, perovskite oxides, transition‐metal sulfides, phosphides, selenides, and metal‐organic frameworks (MOFs) have been extensively explored. [ 2e,10 ] Their impressive electrocatalytic performance capabilities make them promising candidates as alternatives to noble metal‐based materials. Some good reviews that provide a fundamental understanding of typical reactions and recent research on noble/transition‐metal‐based functional materials have been provided.…”

Electronic modulation and interface engineering of electrospun nanomaterials‐based electrocatalysts toward water splitting

“…For the development of high‐performance water splitting electrocatalysts, the modulation of the electronic structure of the catalysts and the construction of heterostructure are also very important. Through the introduction of heteroatom or vacancies, electron transfer will take place between different atom or vacancy groups, resulting in the modulation of the electronic structure 41 . In addition, the construction of a heterostructure with an interface effect leads to a contact of two distinctive phases, constituting more active centers and potentially tuning its electronic interaction 8 .…”

“…Through the introduction of heteroatom or vacancies, electron transfer will take place between different atom or vacancy groups, resulting in the modulation of the electronic structure. 41 In addition, the construction of a heterostructure with an interface effect leads to a contact of two distinctive phases, constituting more active centers and potentially tuning its electronic interaction. 8 Thus, the modulated electronic structure causes the improved water dissociative adsorption or reaction intermediate desorption, which accelerate the electrocatalytic performance for water splitting.…”