Reconstruction of Highly-Defective MgO and Exceptional Photochemical Activity on CO2 Upgrade in Aqueous Solution

Defects on metal oxide have attracted extensive attention in photo-/electrocatalytic CO2 reduction. Herein, porous MgO nanosheets with abundant oxygen vacancies (V(o)s) and three-coordinated oxygen atoms (O-3c) at corners are reported, which reconstruct into defective MgCO3 & BULL;3H(2)O exposing rich surface unsaturated -OH groups and vacancies to initiate photocatalytic CO2 reduction to CO and CH4. In consecutive 7-cycle tests (each run for 6 h) in pure water, CO2 conversion keeps stable. The total production of CH4 and CO attains & AP;367 & mu;mol g(cata)(-1) h(-1). The selectivity of CH4 gradually increases from & AP;3.1% (1(st) run) to & AP;24.5% (4(th) run) and then remains unchanged under UV-light irradiation. With triethanolamine (3.3 vol.%) as the sacrificial agent, the total production of CO and CH4 production rapidly increases to & AP;28 000 & mu;mol g(cata)(-1) in 2 h reaction. Photoluminescence spectra reveal that V(o)s induces the formation of donor bands to promote charge carrier seperation. A series of trace spectra and theoretical analysis indicate Mg-V-o sites in the derived MgCO3 & BULL;3H(2)O are active centers, which play a crucial role in modulating CO2 adsorption and triggering photoreduction reactions. These intriguing results on defective alkaline earth oxides as potential photocatalysts in CO2 conversion may spur some exciting and novel findings in this field.

Automated summary

Porous MgO nanosheets with abundant defects are reported as potential photocatalysts for CO2 reduction. The derived defective MgCO3·3H(2)O shows stable CO2 conversion and increased selectivity towards CH4 under UV-light irradiation. The presence of oxygen vacancies (V(o)s) promotes charge carrier separation and the Mg-V-o sites play a crucial role in CO2 adsorption and photoreduction reactions. These findings may lead to novel discoveries in the field of CO2 conversion.