Coupling Methanol Oxidation with Hydrogen Evolution on Bifunctional Co-Doped Rh Electrocatalyst for Efficient Hydrogen Generation

Abstract

Efficient hydrogen production from electrochemical overall water splitting requires high-performance electrocatalysts for hydrogen evolution reaction (HER) and a fast oxidation reaction to replace sluggish oxygen evolution reaction. Herein, Co-doped Rh nanoparticles are thus grown on carbon black using Co nanosheets as the bridge. These nanoparticles with a size of ≈1.94 nm exhibit the overpotential of as low as 2 mV at 10 mA cm−2 for the HER, and a mass activity of as high as 889 mA mg−1 for the methanol oxidation reaction (MOR) in alkaline media. As confirmed by density functional theory simulations, such excellent activity originates from Co-doping, which reduces reaction energy barriers for both the rate-determining step of a Volmer process during the HER and the conversion of *CO to COOH* during the MOR (namely the enhanced adsorption of H2O and COOH*). Coupling boosted HER on the cathode with accelerated MOR on the anode, efficient H2 generation is achieved. This two-electrode cell only requires a cell voltage of 1.545 V at 10 mA cm−2 with impressive long-life cycling stability. Such performance even outperforms that of commercial Pt/C || IrO2 cell. This study offers a new strategy to achieve efficient HER from overall water splitting.