CuO and CuPO (Cu2P2O7 and Cu3(PO4)2) as precursors are in suit construction two distinct copper-based active sites during the NO3RR reaction: Cu1+/Cu0 (derived from CuO) and Cu2+/Cu0 (derived from CuPO). Cu1+/Cu0 is the key to achieving high activity and high selectivity. Combining online DEMS and in situ FT-IR spectroscopy with DFT calculations, the reaction mechanism of Cu1+/Cu0 is confirmed.
Abstract
Electrocatalytic nitrate reduction reaction (NO3RR) as a sustainable nitrogen cycle regulation strategy provides a new pathway to achieve carbon neutrality goals. In this study, CuO, Cu2P2O7 and Cu3(PO4)2 (CuPO) are synthesized as pre-catalysts via a sol-gel process for NO3RR, in which CuO exhibits excellent NH3 yields of 8.16 mg h−1 mgcat
−1 (FE = 95.72%, -0.95 V vs. RHE) compared to Cu2P2O7 (7.33 mg h−1mgcat
−1, 94.88%) and Cu3(PO4)2 (6.53 mg h−1mgcat
−1, 92.04%). The combination of in situ Raman and XPS spectra reveal that the pre-catalyst surface is reconfigured to form stable active sites of Cu1+/Cu0 (CuO-derived) and Cu2+/Cu0 pairs (CuPO-derived) during the NO3RR process. Tracking the evolution of intermediates using online differential electrochemical mass spectrometry (DEMS) spectra and in situ Fourier transform infrared spectroscopy (FT-IR) spectra reveal that Cu1+/Cu0 pairs possess rapid catalytic kinetics for the conversion of *NO3
− to *NO2
−. Density functional theory (DFT) calculations confirm that Cu1+/Cu0 exhibits a lower potential-determining step, and its exceptional *H generation and enrichment capabilities promote further hydrogenation reactions, thereby achieving excellent activity and selectivity in NH3 production via NO3RR. This study reveals the distinct advantages of reconstructed active sites in Cu-based catalysts during NO3RR, providing guidance for designing other advanced catalysts.
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