Atomically dispersed rhodium on MXenes via microwave solvothermal strategy for high-performance hydrogen evolution catalysis

This work introduces a new microwave-assisted solvothermal method for decorating nanoflakes of transition metal carbides Ti₃C₂ and V₂C (MXenes) with rhodium single-atom catalytic sites, significantly improving hydrogen evolution reaction (HER) electrocatalytic efficiency. The results show that microwave treatment does not significantly alter the nanoflake structure but promotes the formation of sub-nanometer-sized Rh catalytic sites. Rh-decorated nanoflakes exhibit superior catalytic performance in acidic, basic, and neutral media compared to pure MXenes. Turnover frequencies (TOF) suggest that the HER catalytic activity of Rh sites is comparable to or higher than that of pure platinum surface atoms. Mutual arrangement of the Gibbs free energy of hydrogen adsorption on the catalytic site, in scenarios with protonated and nonprotonated terminal groups of the nanoflake, can serve as an electrocatalytic efficiency criterion. A combined analysis of catalytic center activity, DFT-calculated core-level shifts, and experimental XPS spectra identifies the most probable structures of the Rh catalytic centers formed through the microwave-assisted solvothermal process. Rh anchored to the oxygen terminals of the MXene nanoflake surface, bonded with two or three oxygen atoms, explains the Rh 3d XPS band with a significant chemical shift and demonstrates excellent electrocatalytic potential.