Spatial construction of rhodium nanocrystals anchored onto TiO2-decorated MXene architectures for enhanced photoelectrocatalytic methanol oxidation

Abstract

The sluggish kinetics of the methanol oxidation reaction largely hinders the practical application of direct methanol fuel cell, which imposes stringent requirements on the anodic catalysts. Herein, we report a rational heterointerface engineering strategy to the spatial construction of a photo-cascade electrocatalyst by in situ anchoring rhodium nanocrystals onto TiO2-decorated Ti3C2Tx MXene (Rh/TiO2–MX) architecture through a combined oxidative etching and solvothermal assembly process. The existence of TiO2 interlayers not only prevents MXene restacking and provides abundant anchoring sites for Rh nanocrystals, but also promotes the adsorption and activation of water molecules to generate hydroxyl species for efficient CO oxidation, while the conductive MXene substrate facilitates rapid electron transfer and enhances interfacial electron interaction. Therefore, the optimized Rh/TiO2-MX catalyst exhibits excellent electrocatalytic performance for methanol oxidation, with an electrochemical active surface area of 122.5 m2 g-1 and a mass activity of 1799.1 mA mg-1, significantly outperforming Rh catalysts supported on bare MXene and conventional carbon substrates. Under visible light irradiation, the mass activity of the catalyst is further enhanced to 2275.0 mA mg-1, representing a 26.5% increase compared to that under dark conditions, which is attributed to the photogenerated electrons that facilitate charge separation and suppress CO adsorption.