Oxygen functionalized diamond nanocone arrays coupling cobalt phthalocyanine for enhanced electrochemical CO₂ reduction

The development of high-efficiency catalysts plays a crucial role in advancing CO₂ electroreduction techniques. Among potential candidates, diamond-based electrocatalysts show promise due to their broad electrochemical windows, which effectively suppress competitive hydrogen evolution and ensure high CO₂ reduction efficiency. In this study, we report an integrated electrode composed of oxygen-terminated diamond nanocone (OD_cone) with CoPc-molecules anchoring (CoPc/OD_cone). The CoPc/OD_cone electrodes exhibited remarkable performance, achieving a maximum Faradaic efficiency (FE) of 94.1% for CO at −0.97 V vs reversible hydrogen electrode (RHE), and maintaining an FE_CO higher than 80% over a wide potential range of −0.67 V to −1.07 V vs RHE. The outstanding performance of the CoPc/OD_cone electrode can be attributed to the synergistic effects between the nanostructured diamond surface and the CoPc catalyst. The hydroxyl-rich nature of the diamond surface facilitates the anchoring of CoPc molecules and bonding with Co atoms in CoPc. Simultaneously, the nanostructured diamond with sharp tips enhances CO₂ adsorption, thereby improving the catalyst's performance. This study provides valuable insights into the utilization of non-metallic carbon materials, particularly diamond, as metal-free catalysts in CO₂ electrochemical reduction and tackles challenges such as low current density and poor Faradaic efficiency, thus contributing to the advancement of more effective catalysts for CO₂ electroreduction. © 2024 Elsevier Ltd.