Engineering Co3O4/CoS2 heterojunction electrocatalyst to promote hydrogenation for highly efficient nitrate-to-ammonia conversion

Electrochemical nitrate reduction has emerged as a sustainable route for green ammonia synthesis. Cobalt oxide exhibits high activity owing to its efficient proton generation from water electrolysis. Nevertheless, the unsynchronized proton supply and nitrogen oxide intermediate conversion results in competing H 2 evolution and reduced ammonia selectivity. To address this issue, we designed a Co 3 O 4 @CoS 2 nano-heterostructure catalyst by introducing CoS 2 (with excellent NO x adsorption performance) via hydrothermal synthesis. Electrocatalytic tests showed that the as-prepared Co 3 O 4 @CoS 2 nanocatalyst achieved a Faradaic efficiency of 99.91 % and an NH 3 yield of 23.97 mg/ (h·cm 2 ) at −0.3 to −0.7 V vs. RHE, significantly outperforming pristine Co 3 O 4 and CoS 2 . Results from in-situ Raman spectroscopy and density functional theory calculations revealed that the superior performance stems from enhanced NO x adsorption/hydrogenation and a reduced reaction energy barrier of Co 3 O 4 @CoS 2 with CoS 2 incorporation. This work proposes a facile and efficient heterostructure construction strategy, offering new insights into the design of electrocatalysts for NH 3 synthesis.