Coupling ceria with dual-phased molybdenum carbides for efficient and stable hydrogen evolution electrocatalysis at large-current-density in freshwater and seawater

In this study, we report a novel self-supported electrode consisting of ceria/molybdenum carbides composite microrods with adjustable crystalline phases and abundant heterostructures on carbon cloth (CeO 2 /Mo x C/CC). The optimized CeO 2 /α-MoC/β-Mo 2 C MRs/CC electrode exhibits very low overpotentials of 22 and 29 mV at 10 mA cm −2 for hydrogen evolution reaction (HER) in alkaline freshwater and seawater, outperforming most of the reported molybdenum carbide-based electrocatalysts. Meanwhile, it could maintain long-term stability for over 100 h at a large current density of 1000 mA·cm −2 . Theoretical study and experimental results reveal that the synergistic effects of α-MoC, β-Mo 2 C, and oxygen vacancy-rich CeO 2 can effectively promote the dissociation of water molecules, tailor the d‐band electronic structure of Mo x C with a thermoneutral hydrogen adsorption free energy , increase the numbers of active sites, and facilitate the vectorial electron transfer, thus achieving an enhanced HER performance. The CeO 2 /α-MoC/β-Mo 2 C MRs/CC electrode displays a potential large-scale application in hydrogen generation.