Au Nanocrystals@Defective Amorphous MnO₂ Nanosheets Core/Shell Nanostructure with Effective CO₂ Adsorption and Activation toward CO₂ Electroreduction\nto CO

Abstract

CO₂ electroreduction (CO₂ER) is a promising\navenue to convert aerial CO₂ into carbonaceous fuels or\nvalue-added chemicals. In this work, we constructed Au nanocrystals@defective\namorphous MnO₂ nanosheets core/shell nanostructure (Au\nNCs@a-MnO₂ NSs) with tunable lateral size of nanosheets\nshell for efficient CO₂ER to CO. The good gas-permeable\nbehavior in the special nanocrystals/defective nanosheets core/shell\nnanostructure expanded the adsorption capacity of CO₂ molecules.\nAu NCs core in Au NCs@a-MnO₂ NSs brought about high electrical\nconductivity and boosted electron transport from the catalyst to adsorbed\nCO₂ molecules, while a-MnO₂ NSs shell with large\nnumbers of oxygen defects favored the activation of CO₂ molecules for the subsequent reduction reaction. The optimal Au\nNCs@a-MnO₂ NSs with ∼60 nm lateral size of nanosheets\nshell output the utmost CO faradic efficiency (FE_CO) of\n90.5% at −0.7 V and remained with a high FE_CO >\n80% from −0.6 to −0.8 V. Meanwhile, Au NCs@a-MnO₂-60 NSs displayed partial current densities of 3.6 mA cm^–2 at −0.7 V and 14.3 mA cm^–2 at −1.0 V for CO. It also exhibited outstanding stability\nwith negligibly decreased current densities after 12 h electrocatalysis\nat −0.5, −0.7, and −0.9 V. The synergy between\nAu NCs core and a-MnO₂ NSs shell is contributed to its\nprominent activity, selectivity, and stability for CO₂ER\nto CO. This work integrates conductivity promotion and defect engineering\nby noble-metal@defective amorphous oxide core/shell nanostructure\ntoward improved CO₂ER.