Amino acid modified melamine foam as solid-state proton donor for CsPbBr3-based S-scheme heterojunction driven photocatalytic CO2 reduction

H2O as a proton source affects the stability of lead halide perovskites, restricting the photocatalytic CO2 reduction reaction (CO2RR). In this paper, l-lysine modified melamine foam (L-MF) is designed as an efficient solid-state proton donor to participate in CO2RR of CsPbBr3-based S-scheme heterojunction. On the one hand, abundant –COOH and –NH2 groups of l-lysine would break easily compared with H2O, which provides adequate protons for CO2RR. Moreover, the functionalized –COOH and –NH2 groups of l-lysine as Lewis base could coordinate with unsaturated Pb2+ of CsPbBr3, which could decrease the defect density of perovskite and improve the charge migration of catalyst. On the other hand, three-dimensional and porous melamine foam as a supporter could achieve gas-solid bi-phase CO2RR system, which contributes to mass transfer efficiency between CO2 gas and catalyst, accelerating CO2 conversion into high value-added fuels. Under sunlight irradiation, product yield of CO2RR reaches 73.47 μmol/g/h for L-MF/CsPbBr3/Bi2WO6, which is 2.8- and 72.7-fold of MF/CsPbBr3/Bi2WO6 (25.93 μmol/g/h) and CsPbBr3/Bi2WO6 powder (1.01 μmol/g/h) with H2O as proton source, suggesting the efficient proton supply for CO2RR from solid-state proton donor. This work could open a new avenue to utilize lead halide perovskites-based catalysts for energy conversion.