Enhanced Electrochemical CO<sub>2</sub> Reduction of Cu@Cu<i><sub>x</sub></i>O Nanoparticles Decorated on 3D Vertical Graphene with Intrinsic sp<sup>3</sup>‐type Defect
Zhipeng Ma, Constantine Tsounis, Priyank V. Kumar, Zhaojun Han, Roong Jien Wong, Cui Ying Toe, Shujie Zhou, Nicholas M. Bedford, Lars Thomsen, Yun Hau Ng, Rose Amal
Abstract
Abstract 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.