Self-supported Hierarchical Nanoporous Cu/Mo@MoOx Hybrid Electrodes as Robust Nonprecious Electrocatalysts for High-efficiency Hydrogen Evolution

Background: The hydrogen evolution reaction is a crucial step in electrochemical water splitting to generate molecular hydrogen with high purity, but it usually suffers from a sluggish reaction kinetics in alkaline media because of additional water dissociation and/or improper adsorption energy of reactive hydrogen intermediates. It is desirable to design highly active and robust nonprecious electrocatalysts as alternatives to state-of-the-art commercially available Pt/C catalysts for large-scale hydrogen production via water-alkali electrolysis. Methods: We developed monolithic nanoporous hybrid electrodes composed of electroactive Mo@MoOx nanoparticles, which are seamlessly integrated on hierarchical nanoporous Cu scaffold (Cu/Mo@MoOx) by making use of a spontaneous phase separation of Mo nanoparticles and subsequently, self-grown MoOx in chemical dealloying. Results: Owing to the unique monolithic electrode architecture, in which the constituent Mo@MoOx nanoparticles work as electroactive sites and the hierarchical nanoporous Cu skeleton serves as fast electron-transfer and mass-transport pathways, the monolithic nanoporous Cu/Mo@MoOx hybrid electrode exhibits superior electrocatalysis in 1 M KOH, with a low Tafel slope of 66 mV dec⁻¹ and outstanding stability. It only takes them ~185 mV overpotential to reach −400 mA cm⁻², ~150 mV lower than that of nanoporous Cu supported Pt/C. Conclusion: The outstanding electrochemical performance and excellent structural stability make nanoporous Cu/Mo@MoOx electrodes attractive alternatives to Pt/C catalysts in alkaline-based devices.