Solution‐phase‐reconstructed Zn‐based nanowire electrocatalysts for electrochemical reduction of carbon dioxide to carbon monoxide

Abstract

The production of CO via electrochemical CO2 reduction has been recognised as a promising technology that overcomes the environmental issues caused by global warming. It also facilitates the conversion of CO2 into energy sources. Earth-abundant Zn is a well-known alternative to noble metal catalysts such as Au and Ag for the electrochemical CO2 reduction to CO. In particular, Zn-based materials in the form of nanowires are potentially applicable as electrocatalysts in the electrochemical CO2 reduction. However, the conventional methods for manufacturing the nanowire structure are difficult as they require harsh conditions such as high temperatures and excess energy. In this study, Zn-based nanowire catalysts are prepared by the facile electrodeposition of Zn nanostructures on a substrate followed by their energy-free solution-phase reconstitution. Further, their electrochemical performance in the CO2 reduction is investigated in a CO2-purged 0.5 M KHCO3 electrolyte. By optimising the deposition conditions, hexagonal Zn (h-Zn) plates with dominant Zn(101) facets, the favoured crystal structure for CO2 reduction, are fabricated on carbon paper. Furthermore, it is found that, during the solution-phase reconstruction over 16 hours, the h-Zn plate transforms to a nanowire owing to the differences between the oxidation rates of different crystal facets and the formation of a hydroxide complex. The activity of the reconstructed Zn-based nanowire catalyst is enhanced further by forming an oxide layer via thermal treatment in a H2 atmosphere. This treatment boosted the reaction kinetics, thereby enhancing the catalyst performance in the CO2 reduction.