Recent advances in selective methanol oxidation electrocatalysts for the co-production of hydrogen and value-added formate†

Abstract

Traditional water splitting is significantly impeded by the sluggish kinetics and large overpotential of the anodic oxygen evolution reaction (OER). Accordingly, replacing the OER with a more thermodynamically favorable organic substance oxidation reaction to combine with the hydrogen evolution reaction (HER) is an innovative strategy to obtain green hydrogen. In this case, the electro-reforming of methanol coupled with the electrochemical HER can realize the energy-saving co-generation of value-added formate and hydrogen. Therefore, controlling the process of methanol oxidation and making it selectively transform to formate have become a worthy topic. Thus far, various catalysts and modification strategies have been developed for the selective methanol oxidation reaction (SMOR). Transition metal-based materials are the most studied catalysts because their moderate catalytic ability can better control the process of methanol oxidation. Electronic structure modulation is the most efficient strategy to improve the SMOR performance of catalysts. However, few systematic reviews on the SMOR have been reported. In light of significant advances achieved recently, herein, we reviewed the recent advances in SMOR electrocatalysts for the co-production of value-added formate and green hydrogen. In particular, the mechanism of the SMOR is initially introduced, including the traditional surface adsorption mechanism and the newly developed lattice oxygen participation mechanism. Subsequently, strategies for catalyst design are analyzed from the aspects of chemical bond activation/inhibition, electronic structure manipulation, dual active site construction, and increasing the number of active sites. Thereafter, performance descriptors involving electrochemical measurements and product detection are discussed to show the basic evaluation criterion, and various catalysts for the SMOR are categorized according to their composition to display the development of catalysts. Finally, conclusions and perspectives are presented. We hope that this comprehensive effort will be helpful in the literature survey of the SMOR and provide inspiration to the SMOR research community, attracting more attention to the electro-upgradation of organic substances coupled with green hydrogen generation.