Defects on metal oxide have attracted extensive attention in photo-/electrocatalytic CO 2 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 MgCO 3 ·3H 2 O exposing rich surface unsaturated -OH groups and vacancies to initiate photocatalytic CO 2 reduction to CO and CH 4 . In consecutive 7-cycle tests (each run for 6 h) in pure water, CO 2 conversion keeps stable. The total production of CH 4 and CO attains ≈367 µmol g cata −1 h −1 . The selectivity of CH 4 gradually increases from ≈3.1% (1 st run) to ≈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 CH 4 production rapidly increases to ≈28 000 µmol 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 MgCO 3 ·3H 2 O are active centers, which play a crucial role in modulating CO 2 adsorption and triggering photoreduction reactions. These intriguing results on defective alkaline earth oxides as potential photocatalysts in CO 2 conversion may spur some exciting and novel findings in this field.
Huixia Li,Shaofan Fang,Junfang Ding,Shaoqing Chen,Liping Li,Guangshe Li
Active-sites play a pivotal role in catalyzing reactions at surfaces, yet engineering these active sites still remains a significant challenge. In this work, hydroxylated MgO nanosheets supported ultrasmall PtNi alloys approximately 2.6(1) nm ( x Pt- y Ni/MgO hydr ) has been investigated via active-site engineering. Experimental results and DFT calculations reveal that electron transfers from Ni to Pt and from hydroxyl groups to Pt 5d-orbitals generate active sites NiPt-(OH) x . In the preferential CO oxidation (CO-PROX) reaction, these active sites on x Pt- y Ni/MgO hydr switch the bicarbonates reaction pathway depending on temperature range. Consequently, the optimal catalyst, 5%Pt-0.5%Ni/MgO hydr , achieves 100% CO conversion at 100 °C, demonstrating a broad temperature operation window (100–200 °C) and excellent durability. The active site engineering approach presented in this study can promote the discovery of more excellent catalysts with the optimal reaction route for various applications.
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