PtAg alloys as an efficient co-catalyst for CO2 deep photoreduction with H2O: Synergistic effects of Pt and Ag

Abstract

Solar driven conversion of CO2 into carbonaceous chemicals is a promising strategy to reduce greenhouse effect and obtain valuable chemical fuel. However, due to the lack of efficient active site, the selective CO2 photoreduction towards multi-electron products remains challenging. Here, we reported PtAg alloy acting as a novel cooperative co-catalyst to boost the CH4 formation from photocatalytic CO2 reduction over HNb3O8 nanosheets (HNb3O8 NS). The PtAg alloy can trap the electrons and improve the charge separation efficiency of the photocatalyst, mitigating the kinetical challenge of eight-electron transfer process for CH4. Further, PtAg alloy acts the synergistic sites for the CO2 reduction, namely, CO2 is reduced on Ag sites into CO intermediates, which then spillover or sequential adsorption on adjacent Pt sites and undergo further hydrogenation into CH4. Due to the synergic effect of Pt and Ag, the optimal PtAg-2/HNb3O8 NS catalyst achieves a selectivity of 74.3% for CH4 with an evolution rate of 93.6 μmol·g−1·h−1, which is about 34.7-fold of pure HNb3O8 NS (2.7 μmol·g−1·h−1). This work provides new insights into the role of synergistic effect of alloy co-catalyst for selective CO2 photoreduction and offers a new idea into the catalytic site design for CH4 formation.