3.3 Copper based
Deng et al. synthesized a Cu2O photocathode coated with a metal-organic framework (MOF) material, Cu3(BTC)2, which could protect the underlying Cu2O from undesirable photocorrosion, facilitate charge separation and electron transfer to active sites, and provide abundant active sites for catalytic CO2reduction.[97] The obtained Cu3(BTC)2/Cu2O photocathode with abundant active sites exhibited a maximum CO selectivity of up to 95 % and STC efficiency of 0.83 % at −2.07 (V vs. Fc/Fc+), surpassing those of a bare Cu2O electrode. Zhao et al. reported a Cu-decorated Co3O­ nanotube electrode for PEC CO2 reduction to formate.[98] Co3O4NTs were first constructed on Co foil by anodization, and Cu electrodeposition was subsequently performed to synthesize metallic Cu-loaded Co3O4 nanotube array electrodes. Because Cu NPs are positively charged due to their interaction with Co3O4, CO2 adsorption on Cu NPs occurs in the form of O-Cu, promoting the protonation of the carbon atom, resulting in the formation of formate. This synergistic effect between Co3O4 NTs and metallic Cu NPs results in remarkable PEC CO2 reduction performance with nearly 100 % selectivity and a maximum production rate of 6.75 mmol·L–1·cm–2 in 8 h PEC process, which is superior to Co3O4 NTs without metallic Cu NPs (Figure 4(I) and (J)). Table 2 summarizes the PEC-CO2RR performance of the co-catalysts.