Compared withother copper catalysts,the (111) OHads peak of Cu nanosheets shown obvious peak intensity, which further confirms that Cu nanosheets are covered by (111) surface. Electrolysis experiments were performed using chronopotentiometry on a potentiostat, with a gas-tight H-cell separated by a piece of Nafion 117 membrane, at room temperature. Hg/HgO electrode was used as reference electrode, and platinum gauze was used as counter electrode (Fig. S5).