Photoreduction of CO2 on Pd-In2O3: Synergistic optimization of progressive electron transfer via amorphous/crystalline Pd and oxygen vacancies

The progressive transfer of photogenerated electrons between the catalyst components and reactants is of great significance for photocatalysis. Amorphous Pd (PdA) and oxygen vacancies (VOs) were simultaneously introduced in Pd-In2O3 exploiting hydrogen-induced amorphization effects; 0.6 wt% Pd-In2O3 exhibited a 4.5-fold increase in activity and a 3.2-fold higher selectivity toward CH3OH + CO (63.62 %) compared with In2O3. Multiple in situ techniques and theoretical calculations revealed that intercomponent electron transfer channels were established via various interface structures formed between PdA or crystalline Pd (PdC) and In2O3; PdA acted as electronic pump, facilitating the transfer and separation of photogenerated electrons, resulting in their subsequent enrichment on the surface of PdA. Simultaneously, PdA acted as electron-donating adsorption site for H2O, increasing the number of electrons received by H2O, further inhibiting the competitive adsorption of H2O and CO2 on VO sites, and promoting the hydrogen evolution reaction. Additionally, the electronic coupling between PdC and VOs could significantly decrease the electron-donating ability of VOs, reducing the number of electrons received by CO2, thus effectively regulating the degree of CO2 reduction. This study employs PdA/PdC and VOs to synergistic optimize the progressive transfer of photogenerated electrons, and presents a novel approach for elucidating the catalytic mechanism.