A Low-Temperature Molecular Precursor Approach to Copper-Based Nano-Sized Digenite Mineral for Efficient Electrocatalytic Oxygen Evolution Reaction

In the urge of designing noble metal-free and sustainable electrocatalysts for oxygen evolution reaction (OER), herein, a mineral Digenite Cu${}_9$S${}_5$ has been prepared from a molecular copper(I) precursor, [{(PyHS) ${}_2$Cu${}^l$ (PyHS)} ${}_2$] (OTf)${}_2$ (1), and utilized as an anode material in electrocatalytic OER for the first time. A hot injection of 1 yielded a pure phase and highly crystalline Cu${}_9$S${}_5$, which was then electrophoretically deposited (EPD) on a highly conducting nickel foam (NF) substrate. When assessed as an electrode for OER, the Cu${}_9$S${}_5$/NF displayed an overpotential of merely 298±3 mV at a current density of 10 mAcm${}^{-2}$ in alkaline media. The overpotential recorded here supersedes the value obtained for the best reported Cu-based as well as the benchmark precious-metal-based RuO${}_2$ and IrO${}_2$ electrocatalysts. In addition, the choronoamperometric OER indicated the superior stability of Cu${}_9$S${}_5$/NF, rendering its suitability as the sustainable anode material for practical feasibility. The excellent catalytic activity of Cu${}_9$S${}_5$ can be attributed to the formation of a crystalline CuO overlayer on the conductive Cu${}_9$S${}_5$ that behaves as active species to facilitate OER. ... mehrThis study delivers a distinct molecular precursor approach to produce highly active copper-based catalysts that could be used as an efficient and durable OER electro(pre)catalysts relying on non-precious metals.