Selective electrocatalytic reduction of nitrate to dinitrogen by Cu2O nanowires with mixed oxidation-state

Abstract

• CuO/Cu 2 O NWs contains switchable oxidation states of Cu (I/II to 0/I). • N 2 selectivity is 99.8% over Cu/Cu 2 O NWs, the highest reported so far. • Cu/Cu 2 O NWs provides active sites for hydrogen/oxygen-adsorbing simultaneously. • Cu/Cu 2 O NWs yields sufficient H* and limit hydrogen bubbles negative effect. • N 2 production based on NO 3 RR is proceeded by H*-mediated route. Selective electrocatalytic nitrate reduction reaction to dinitrogen is a promising water treatment technology to manage nitrate. While, a lack of efficient electrode remains the primary hurdle for achieving the goal. For non-noble electrode, the strong adsorption of oxygen atoms on Cu resulted in low selectivity and inducing nitrite accumulation during the long-term operation. Herein, it is found that Cu 2 O nanowires with mixed oxidation-state can selective reduction of nitrate to dinitrogen. CuO-coated Cu 2 O nanowires (CuO/Cu 2 O NWs) was electrochemically converted into Cu/Cu 2 O NWs for hydrogen/oxygen-adsorbing which was verified by In-situ infrared spectro-electrochemical experiments. H 2 split and H*-adsorbing of Cu/Cu 2 O are desired to yield sufficient H* and limit hydrogen bubbles negative effect. Online differential electrochemical mass spectrometry confirmed dinitrogen generation over Cu/Cu 2 O NWs with over 99.8% selectivity. Computational studies suggest that active Cu/Cu 2 O NWs reduces the free energy changes associated with both nitrate activation and N − N coupling. Energetically favorable pathways for dinitrogen production based on nitrate reduction are proposed herein and the origin of this selective dinitrogen formation is clarified.