High-Performance Nanostructured MoS<sub>2</sub> Electrodes with Spontaneous Ultralow Gold Loading for Hydrogen Evolution
Eliott P. C. Higgins, Athanasios A. Papaderakis, Conor Byrne, Rongsheng Cai, Amr Elgendy, Sarah J. Haigh, Alex S. Walton, David J. Lewis, Robert A. W. Dryfe
Abstract
The scarcity and cost of noble metals used in commercial electrolyzers limit the sustainability and scalability of water electrolysis for green hydrogen production. Herein, we report the ultralow loading of Au nanoparticles onto MoS<sub>2</sub> electrodes by the spontaneous process of galvanic deposition. AuNP@MoS<sub>2</sub> electrode synthesis was optimized, and electrodes containing the smallest Au nanoparticle diameter (2.9 nm) and the lowest Au loading (0.044 μg cm<sup>–2</sup>) exhibited the best overall and intrinsic electrocatalytic performance. This enhancement is attributed to an increased Au–MoS<sub>2</sub> interaction with smaller nanoparticles, making the MoS<sub>2</sub> electrode more n-type. DC electrochemical characterization for the AuNP@MoS<sub>2</sub> electrodes showed an exchange current density of 7.28 μA cm–2 and an overpotential at 10 mA cm–2 of −323 mV. These values are 4.5 times higher and 100 mV lower than those of the unmodified MoS<sub>2</sub> electrode, respectively. Electrochemical AC experiments were used to evaluate the electrodes’ intrinsic catalytic activity, and it was shown that the AuNP@MoS<sub>2</sub> electrodes exhibited an enhanced activity by as much as 3.5 times compared with MoS2. Additionally, the turnover frequency as estimated by the reciprocal of the R<sub>ct</sub>C<sub>dl</sub> product, the latter calculated from the AC data, is estimated to be 58.8 s<sup>–1</sup> and is among one of the highest reported for composite MoS<sub>2</sub> materials.