Efficient electrochemical N2 fixation by dopedoxygen-induced phosphorus vacancy defects on copper phosphide nanosheets

Fig. 1 (a) Schematic of the synthesis procedure of cuprous phosphides; (b) XRD patterns of CFC and RO-Cu3P/CFC; (c) and (d) SEM images of RO-Cu3P/CFC; (e) TEM image of RO-Cu3P/CFC; the inset in (e) shows the SAED pattern of RO-Cu3P/CFC; (f) HRTEM image of RO-Cu3P; (g) SEM-EDS elemental mapping images of RO-Cu3P/CFC.Fig. 2 (a) EDX spectra showing the changes in the elemental composition of the RO-Cu3P/CFC, O-Cu3P/CFC and Cu3P/CFC electrodes, (b–d)high resolution Cu 2p, P 2p, and O 1s XPS spectra of RO-Cu3P/CFC, O-Cu3P/CFC and Cu3P/CFC, (e) Raman spectra of commercial CuO,commercial Cu2O, RO-Cu3P/CFC, O-Cu3P/CFC and Cu3P/CFC, (f) Cu L3,2-edge XAS spectra of Cu, Cu2O, RO-Cu3P/CFC, O-Cu3P/CFC andCu3P/CFC.Fig. 3 (a) Linear sweep voltammetry curves measured in a N2- or Ar-saturated 0.1 M Na2SO4 (pH 3, adjusted by H2SO4) aqueous solution for RO-Cu3P/CFC electrode, (b) chronoamperometry results at the corresponding applied potentials, (c) production rates of ammonia and hydrazine hydrate formation and corresponding FEs using RO-Cu3P/CFC electrode at each given potential, (d) 1 H NMR spectra of the yielded 14NH4 + and 15NH4 + from 14N2 and 15N2 feeding gases and corresponding standards, (e) recycling stability test of the RO-Cu3P/CFC electrode at -0.3 V (vs. RHE) in N2-saturated electrolyte solution with a reaction time of 2 h for each recycling experiment, (f) NH3 and N2H4 yields of the RO-Cu3P/CFC during durability measurements for 10 h.Fig. 4(a) NH3 and N2H4 production rates on Cu/CFC, Cu2O/CFC, Cu3P/CFC and RO-Cu3P/CFC electrodes, (b) the proposed reaction pathwayfor the formation of NH3 and N2H4 from molecular dinitrogen using RO-Cu3P/CFC electrode as a catalyst, (c) free-energy diagrams of NRR onthe surface vacancies of RO-Cu3P catalysts with difffferent concentrations of doped oxygen.