Asymmetric Triple-Atom Sites Confined in Ternary Oxide Enabling Selective CO2 Photothermal Reduction to Acetate

Light-induced heat is largely neglected in traditional photocatalytic systems, especially for the thermodynamically and kinetically challenging CO2 reduction to C2 fuels. Herein, we first design asymmetric Metal1-O-Metal2 triple-atom sites confined in phenakite to facilitate C-C coupling and employ photoinduced heat to increase molecular thermal vibration and accelerate CO2 reduction to C2 fuels. Using O-vacancy-rich Zn2GeO4 nanobelts as prototypes, quasi in situ Raman spectra disclose the Zn-O-Ge triatomic sites are likely the reactive sites. Density functional theory calculations reveal that the asymmetric Zn-O-Ge sites could promote C-C coupling through inducing distinct charge distributions of neighboring C1 intermediates, whereas the created O vacancies could lower the energy barrier of the rate-determining hydrogenation step from 1.46 to 0.67 eV. Catalytic performances under different testing conditions demonstrate that light initiates the CO2 reduction reaction. In situ Fourier-transform infrared spectra and D2O kinetic isotopic effect experiments disclose that light-induced heat kinetically triggers C-C coupling and accelerates OCCO* hydrogenation via providing abundant hydrogen species. Consequently, in a simulated air atmosphere under 0.1 W/cm2 illumination at 348 K, the O-vacancy-rich Zn2GeO4 nanobelts demonstrate an acetate output of 12.7 μmol g-1 h-1, a high acetate selectivity of 66.9%, a considerable CO2-to-CH3COOH conversion ratio of 29.95%, and a stability of up to 220 h.