Nickel/Lanthanide Oxide Heterostructures for Sulfide-Resistant Hydrogen Evolution Electrocatalysis

Coupling sulfide oxidation with hydrogen evolution reaction (HER) is an alternative method of hydrogen production with ultrahigh energy efficiency using waste sulfide recovered from fossil fuel refining. However, this technology demands either membrane separation to prevent sulfide tunneling or a sulfide-resistant HER. Considering the great difficulty in constructing durable membranes in alkaline sulfide-based electrolytes, creating sulfide-resistant electrocatalysts is a more viable option, but typical metallic catalysts suffer from devastating sulfide poisoning. Herein, we created nickel/lanthanide oxide heterostructure catalysts with high HER activity, durability, and sulfide resistance, especially under high-current operating conditions. Among the lanthanide series, the oxide of earlier elements, such as lanthanum, demonstrated higher sulfide resistance and higher activities in sulfide-based electrolytes. The combinatory analysis of kinetics, impedance spectroscopy, and Raman spectroscopy revealed the major contribution of sulfide resistance from the retarded sulfidation process only pertinent to the surface, maintaining the core Ni/La 2 O 3 structure for sustained hydrogen evolution. The surface-transformed nickel sulfide (NiS) can also form the NiS/La 2 O 3 heterostructure that outperformed pure sulfide counterparts, contributing to the maintained long-term activity. This work points out the significance of sulfide resistance for sulfide-driven hydrogen production technology and provides a promising cathode solution for the membrane-less electrolyzer.