Fig. 3: Structural evolution investigation of CuPO and CuO catalysts during CO2RR.
In situ Raman spectra of a Cu3(PO4)2 and b CuO catalysts, respectively, during CO2RR at −1.40 V in CO2-saturated 0.1 M KHCO3, suggesting the existence of Cu3(PO4)2 and the disappear of CuO during CO2RR. XAFS characterization of c the normalized Cu K-edge operando XANES spectra, d Fourier-transformed Cu K-edge EXAFS spectra, and e, f Calculated ratio of Cu oxidation states in e CuO and f Cu3(PO4)2 catalysts from linear combination fitting with respect to time during 30 min of reaction at −1.45 V. The in situ Raman spectra along with operando XAFS analysis demonstrate the coexistence of Cu2+ and Cu0 components in Cu3(PO4)2 and the reductive process of oxide Cu species to the metallic Cu0 states in the CuO control sample. g Morlet WT of the k3-weighted operando EXAFS data for the Cu3(PO4)2 and CuO samples with standard Cu foil and CuO powder as controls, suggesting the coexistence of Cu–O and Cu–Cu bond in Cu3(PO4)2 during CO2RR.
