Evaluating the impact of anodic oxidation reactions on water splitting using Prussian blue analog-derived metal-(oxy)hydroxides

Abstract

Herein, we have evaluated the performance of Prussian blue analog (PBA)-derived Fe–Co(O)OH for the anodic oxidation of a series of organic and inorganic compounds (substituted benzyl alcohols, aliphatic alcohols, substituted benzyl amines, phenol, urea, and hydrazine). The effect of different anodic oxidation reactions (AORs) on the production of cathodic H₂, generation of value-added products, and requirement of potential for the electrochemical process has been considered. Special attention has been provided to achieve an industrial-scale current density for AORs avoiding the interference from the oxygen evolution reaction (OER) and produce value-added chemicals with a faradaic efficiency (FE) > 90%. Fe–Co(O)OH achieved industrial-scale current density for all AORs without any interference from the OER. Among all the AORs, hydrazine oxidation was found to be suitable in terms of required potential and hydrogen production while the oxidation of benzyl alcohol (BA) and benzyl amine (BAm) led to the most promising performance for value-added product formation. The anodic BA (BAm) oxidation achieved 400 mA cm⁻² current density at 1.47 V (1.49 V) vs. RHE with 100% selectivity for benzoic acid (FE = 98.3 ± 1.1%) and cyanobenzene (FE = 97.5 ± 1.2%). Moreover, the replacement of the OER with AORs improved the H₂ evolution efficiency significantly. The XAS study also showed the modulated electronic and atomic structure of the electrocatalyst after AORs.