Facile Fabrication of a Foamed Ag 3 CuS 2 Film as an Efficient Self-Supporting Electrocatalyst for Ammonia Electrolysis Producing Hydrogen.

Ammonia (NH ₃ ) is one of the hydrogen carriers that has received extensive attention due to its high hydrogen content and carbon-free nature. The ammonia electro-oxidation reaction (AOR) and the liquid AOR (LAOR) are integral parts of an ammonia-based energy system. The exploration of low-cost and efficient electrocatalysts for the AOR and LAOR is very important but very difficult. In this work, a novel self-supporting AOR and LAOR bifunctional electrocatalyst of a Ag ₃ CuS ₂ film is synthesized by a simple hydrothermal method. The Ag ₃ CuS ₂ film without a substrate shows efficient catalytic activity and enhanced stability for NH ₃ electrolysis in both aqueous ammonia solution and liquid ammonia, including an onset potential of 0.7 V for the AOR and an onset potential of 0.4 V for the LAOR. The density functional theory calculations prove that compared to Cu atoms, Ag atoms with appropriate charge density on the surface of Ag ₃ CuS ₂ are more electrocatalytically active for NH ₃ splitting, including the low energy barrier in the rate-determining *NH ₃ dehydrogenation step and the spontaneous tendency in the N ₂ desorption process. Overall, the foamed Ag ₃ CuS ₂ film is one of prospective low-cost and stable electrocatalysts for the AOR and LAOR, and the self-supporting strategy without a substrate provides more perspectives to tailor more meaningful and powerful electrocatalysts.