Highly Selective and Durable CO Production via Effective Morphology and Surface Engineering of ZnO Electrocatalysts

The present work demonstrates the morphological and Ag doping effects of ZnO electrocatalysts toward electrochemical CO2 reduction reaction (ECRR). To achieve this, three electrocatalysts, i.e., Nanosphere (0D), Nanorod (1D), and Nanosheet (2D), were synthesized via a facile hydrothermal method, and their ECRR performance was evaluated. As an optimal electrocatalyst, the ZnO Nanorod showed unidirectional growth, higher active surface area and roughness factor compared to Nanosphere and Nanosheet electrocatalysts, which led to a high selectivity for CO up to 68% at a high partial current density of 80 mA·cm–2, maintaining stable performance up to 4 h. Further, to enhance CO selectivity, the Ag doping strategy is employed. With optimal Ag doping (1.0 atom %) in the ZnO Nanorod electrocatalyst, it showed boosted CO selectivity of 91% at a high partial current density of 93.4 mA·cm–2 with stable performance for up to 10 h. This significant enhancement in the ECRR performance using the ZnO electrocatalyst could be attributed to the morphological features (Nanorod) and the enhanced electronic conductivity with Ag doping. Based on these results, it can be inferred that the simultaneous engineering of morphological features and Ag doping can be an effective way to improve the ECRR performance and CO selectivity.