Exploring anodic oxidation reactions in hybrid water electrolysis: special emphasis on substrate choice

Abstract

Hybrid water electrolysis (HWE) stands out as a promising avenue for simultaneously producing high-value-added chemicals and clean H₂ fuel. In HWE, instead of the oxygen evolution reaction (OER) typical in electrochemical water splitting, the anodic oxidation reaction (AOR) takes place, leading to the conversion of organic/inorganic compounds at the anode into valuable chemicals, while the hydrogen evolution reaction (HER) generates H₂ at the cathode. The recent literature has seen a surge in papers exploring various AORs utilizing organic and inorganic substrates to supplant the OER, yielding both high-value chemicals and H₂. These studies highlight catalyst properties, conversion rates, chemical production, and H₂ generation. Additionally, numerous reviews delve into the fundamentals, catalytic design, progress, and applications of catalysts in hybrid water electrolysis. However, a gap remains in identifying the most suitable organic/inorganic substrates for the AOR to replace the OER, considering factors such as potential enhancement, maximum current density achieved, substrate conversion, selectivity, interference from the OER, improved H₂ production, energy efficiency, industrial scalability, and high-value chemical formation. This review aims to address this gap by systematically discussing the fundamentals of hybrid water electrolysis and key parameters of the AOR, crucial for replacing the OER. It examines suitable AORs in terms of value-added chemical production, conversion rates, selectivity, H₂ generation, potential improvement, and industrial applicability through pioneering examples. Furthermore, it comprehensively explores the merits and drawbacks of hybrid water electrolysis, along with associated challenges and prospects in this domain.