Enhanced Electrochemical CO 2 Reduction of Cu@Cu x O Nanoparticles Decorated on 3D Vertical Graphene with Intrinsic sp 3 ‐type Defect

Defective 3D vertical graphene (VG) with a relatively large surface area, high defect density, and increased surface electrons is synthesized via a scalable plasma enhanced chemical vapor deposition method, together with a postsynthesis Ar‐plasma treatment (VG‐Ar). Subsequently, Cu@Cu x O nanoparticles are deposited onto VG‐Ar (Cu/VG‐Ar) through a galvanostatic pulsed electrodeposition method. These Cu@Cu x O nanocatalyst systems exhibit a superior electrochemical CO 2 reduction performance when compared to Cu‐based catalysts supported on commercial graphene paper or pristine VG without postsynthesis Ar‐plasma treatment. The Cu/VG‐Ar achieves the highest CO 2 reduction Faradaic efficiency of 60.6% (83.5% of which are attributed to liquid products, i.e., formate, ethanol, and n‐propanol) with a 5.6 mA cm −2 partial current density at −1.2 V versus reversible hydrogen electrode (RHE). The improved CO 2 reduction performance of Cu/VG‐Ar originates from the well‐dispersed Cu@Cu x O nanoparticles deposited on the defective VG‐Ar. The intrinsic carbon defects on VG‐Ar can suppress the hydrogen evolution reaction as well as tune the interaction between VG and Cu@Cu x O, thus impeding the excessive oxidation of Cu 2 O species deposited on VG‐Ar. The defective VG‐Ar and stabilized Cu@Cu x O enhances CO 2 adsorption and promotes electron transfer to the adsorbed CO 2 and intermediates on the catalyst surface, thus improving the overall CO 2 reduction performance.