Selective CO2 Photoreduction to CH4 via Pdδ+-Assisted Hydrodeoxygenation over CeO2 Nanosheets

Here, noble-metal-doped two-dimensional metal oxide nanosheets are designed to realize selective CO2 photoreduction to CH4. As a prototype, Pd-doped CeO2 nanosheets are fabricated, where the active sites of Pd delta+ (2<delta<4) and Ce3+-O-v are revealed by quasi in situ X-ray photoelectron spectra and in situ electron paramagnetic resonance spectra. Moreover, in situ Fourier-transform infrared spectra of D2O photodissociation and desorption verify the existence of the Pd-OD bond, implying that Pd delta+ sites can participate in water oxidation to deliver H* species for facilitating the protonation of the intermediates. Furthermore, theoretical calculations suggest the Pd doping could regulate the formation energy barrier of the key intermediates CO* and CH3O*, thus making CO2 reduction to CH4 become the favorable process. Accordingly, Pd-doped CeO2 nanosheets achieve nearly 100 % CH4 selectivity of CO2 photoreduction, with the raising CH4 evolution rate of 41.6 mu mol g(-1) h(-1).