Electrochemical CO2 reduction: Advances, insights, challenges, and future directions

Abstract

The increasing energy demand, the depletion of fossil fuels, and the threat of global warming are significant and urgent issues for humanity. The electrochemical reduction of CO₂ (ECR) using renewable energy sources to produce fuels and chemicals such as carbon monoxide, methane, ethylene, ethane, formate, methanol, ethanol, and propanol, presents a sustainable and carbon-neutral alternative to fossil fuels. However, several challenges impede stable, selective, efficient, and large-scale production of desired products, especially longer-chain hydrocarbons (C₂₊ products). These challenges include a limited understanding of reaction kinetics, the complex role of process parameters, a shortage of effective electrocatalysts, and unoptimized electrolyzer designs. The present review summarizes detailed insights into the scientific and technological facets of ECR, focusing on established practices and offering a comprehensive overview of known ECR catalysts. It includes a brief historical context and explores methods for studying the reaction kinetics including operando, electrochemical, and computational techniques. The review examines the intertwined process factors influencing ECR and underscores the evolving designs of electrolyzers to manage these factors effectively. It discusses conventional and innovative approaches to catalyst design and addresses the challenges related to the stability of the catalysts. Recent advancements and potential future directions for CO₂ ECR studies are also highlighted.