The role of morphology on the electrochemical CO₂ reduction performance of transition metal-based catalysts

The continued increase in population and the industrial revolution have led to an increase in atmospheric carbon dioxide (CO₂) concentration. Consequently, developing and implementing effective solutions to reduce CO₂ emissions is a global priority. The electrochemical CO₂ reduction reaction (CO₂RR) is strongly believed to be a promising alternative to fossil fuel-based technologies for the production of value-added chemicals. So far, the implementation of CO₂RR is hindered by associated electrochemical reactions, such as low selectivity, hydrogen evolution reaction (HER), and additional overpotential induced in some cases. As a result, it is necessary to conduct a timely evaluation of the state-of-the-art strategies in CO₂RR, with a focus on the engineering of the electrocatalytic systems. Catalyst morphology is one factor that plays a critical role in overcoming these drawbacks and significantly contributes to enhancing product selectivity and Faradaic efficiency (FE). This review article summarizes the recent advances in the rational design of electrocatalysts with various morphologies and the influence of these morphologies on CO₂RR. To compare literature findings in a meaningful way, the article focuses on results reported under a well-defined period and considers the first three rows of the d-block metal catalysts. The discussion typically covers the design of nanostructured catalysts and the molecular-level understanding of morphology-performance relationship in terms of activity, selectivity, and stability during CO₂ electrolysis. Among others, it would be convenient to recommend a comprehensive discussion on the morphologies of single metals and heterostructures, with a detailed emphasis on their impact on CO₂ conversion.