NiSe/NiSe on nickel foam as an ultra-high-rate HER electrocatalyst: common anion heterostructure with built-in electric field and efficient interfacial charge transfer.

One grand challenge in green hydrogen production is to design efficient HER electrocatalysts for high-rate alkaline water electrolysis. Nickel chalcogenide coatings on nickel foam (NF) are promising HER electrocatalysts, but their high-rate performances are yet to be improved. The current work reports a NiSe/NiSe@NF for alkaline HER, which requires an overpotential of only 336 mV to achieve an ultra-high current density of 1250 mA cm, outperforming commercial Pt/C. The low onset potential of NiSe/NiSe@NF is attributed to its morphology, and high surface area, as well as multiple active sites and electronic structure modulation because of the heterostructure. While these features are well-known within the current knowledge framework, new understandings are proposed on its superior high-rate performance. The common-anion feature offers abundant interfacial Ni-Se bonding and low resistance for efficient interfacial charge transfer, whereas the heterovalent-Ni-cation in the heterostructure results in a built-in electric field that further enhances the high-rate performance. This work provides new insights on both the mechanistic and methodological aspects of designing high-performance electrocatalysts operating at high current densities.