Economic evaluation and catalyst design for a hybrid water electrolysis system

Abstract

As a zero-carbon way to produce hydrogen, traditional water electrolysis is hindered by the sluggish kinetics of the oxygen evolution reaction (OER), which results in a high voltage input. The hybrid water electrolysis (HWE), which replaces the OER with economically viable electro-oxidation reactions, could significantly lower the required voltage and, in turn, enhance energy conversion efficiency. Moreover, the HWE system is easy to integrate into the currently available industrial processes to minimise their production cost. This review systematically categorizes three major types of alternative oxidation reactions based on their reaction purposes and products: conversion reactions (targeting the selective transformation of valuable substrates), degradation reactions (aimed at breaking down pollutants or hazardous compounds), and hydrogen carrier oxidation reactions (utilizing hydrogen-rich compounds such as ammonia to facilitate energy conversion). The economic feasibility, environmental benefits and relevant catalyst design strategies of these reactions are also explored. Finally, it summarizes the current research status of hybrid water electrolysis and discusses the challenges encountered, as well as prospects for development.