Enhanced single-atom cobalt layer in MAX phase for biomass electrooxidation integrated with hydrogen evolution

MAX phases have attracted considerable interest due to their structural diversities and potential applications. More than 150 MAX phases have been synthesized, especially expanding the range of A-site atoms from traditional main group elements to subgroup elements with outer layer d electronic structure. However, the functional applications for MAX phases remain somewhat limited. The A-site elements in MAX phases can amplify their inherent properties, transforming primary structural materials into multifunctional materials. As highly catalytic elements, introducing cobalt into the A-site of MAX phases can reveal surprising catalytic activities. Hence, the MAX phase with single-atom-thick cobalt layers was synthesized via an A-site alloying strategy in this work. The obtained V 2 (Sn 2/3 Co 1/3 )C MAX phase demonstrates efficient electrocatalysis in 5-hydroxymethylfurfural (HMF) oxidation reaction along with hydrogen evolution reaction (HER). In-situ electrochemical studies discover that HMF can prevent the self-reconstruction of MAX phase and oxygen evolution reaction (OER). The overall reaction reaches 94.4% yield to 2,5-furandicarboxylic acid (FDCA) at 1.60 V. Density functional theory calculations suggest that the Co-Sn bimetallic synergy in the A-site promotes the reaction. This groundbreaking investigation into using MAX phases for biomass upgrading highlights their potential in green chemistry and beyond.