Reconstruction of Highly-Defective MgO and Exceptional Photochemical Activity on CO 2 Upgrade in Aqueous Solution

Defects on metal oxide have attracted extensive attention in photo-/electrocatalytic CO reduction. Herein, porous MgO nanosheets with abundant oxygen vacancies (V s) and three-coordinated oxygen atoms (O ) at corners are reported, which reconstruct into defective MgCO ·3H O exposing rich surface unsaturated -OH groups and vacancies to initiate photocatalytic CO reduction to CO and CH . In consecutive 7-cycle tests (each run for 6 h) in pure water, CO conversion keeps stable. The total production of CH and CO attains ≈367 µmol g h . The selectivity of CH gradually increases from ≈3.1% (1 run) to ≈24.5% (4 run) and then remains unchanged under UV-light irradiation. With triethanolamine (3.3 vol.%) as the sacrificial agent, the total production of CO and CH production rapidly increases to ≈28 000 µmol g in 2 h reaction. Photoluminescence spectra reveal that V s induces the formation of donor bands to promote charge carrier seperation. A series of trace spectra and theoretical analysis indicate Mg-V sites in the derived MgCO ·3H O are active centers, which play a crucial role in modulating CO adsorption and triggering photoreduction reactions. These intriguing results on defective alkaline earth oxides as potential photocatalysts in CO conversion may spur some exciting and novel findings in this field.