FIGURE 4 Electrochemical performances of co-catalysts for CO2 reduction. (A) Fabrication process of Nanoporous Au thin films on Si Photoelectrodes. (B) Total current densities of Au thin films. (C) CO FEs at various potentials with different RA treatment times. Reproduced with the permission.[90]Copyright 2016, John Wiley and Sons. (D) LSV curve and (E) FECO of Au/p-Si, Au/TiO2/p-Si, Au/n+p-Si, and Au/TiO2/n+p-Si. (F) Free energy diagram of CO2RR over Au and Au/TiO2, respectively. Reproduced with the permission.[92] Copyright 2021, John Wiley and Sons. (G) FEs of formate, H2, and CO on Si/Bi-15 min. (H) Faradaic efficiencies for formate, H2, and CO on p-Si/Bi. Reproduced with the permission.[95]Copyright 2018, Materials Today Chemistry. (I) Formate yield on Co3O4 NTs electrode. (J) Formate yield on Cu-Co3O4 NTs electrode. Reproduced with the permission.[98] Copyright 2015, American Chemical Society