In situ topotactic formation of the pn-type inorganic intergrowth bulk heterojunction NiO(Al)/CuO(Ni,Al) for photocatalytic CO2 methanation

Considering that photosynthetic CH4 seems to have a high energy density, it serves as a powerful way for storing renewable energy. In this work, a potential pn-type inorganic intergrowth bulk heterojunction (pn-IIBH) NiO(Al)/CuO(Ni,Al) was designed and obtained by the precursor CuNiAl-layered double hydroxides with two-stage topological pyrolysis (TTP) method. The microstructure was investigated in detail EXAFS to understand in-situ topotactic formation of the IIBH. Then, by using ISI-XPS, and fs-TAS, the transfer mechanism of the photogenerated electrons in NiO(Al)/CuO(Ni,Al) was explored which met pn-type heterojunction. Furthermore, it was screened for CO2 photoreduction to target CH4 (86.59 μmol/g·h) and O2 (150.84 μmol/g·h) from H2O and the selectivity of CH4 reached more than 87.13%. Finally, in-situ IR and DFT calculation demonstrated that CO2 methanation by the hydrogenation pathway occurred and the Ni doping in the pn-IIBH activated CO2 adsorption more effectively. This work offers an approach to photocatalysis development in CO2 methanation.