Development of non-noble metal single atom catalysts for proton exchange membrane-based acidic carbon dioxide electrolyzer

Abstract

The utilization of fossil fuels has provided comfort to humanity, yet the extensive release of carbon dioxide has led to a rise in global temperatures. Presently, electrochemical CO$_2$ reduction reactions are extensively explored using diverse catalysts. However, the initial application in a basic environment to suppress hydrogen evolution reactions has resulted in challenges related to carbon efficiency and product cross-over issues due to anion penetration through anion exchange membrane. In this research, we have synthesized a highly selective nickel single-atom catalyst by incorporating nitrogen atoms onto a carbon black support. The effective dispersion of nickel atoms is confirmed through various analytical techniques. EXAFS analysis has revealed a metal-nitrogen peak at 1.6 Å without the typically observed metal-metal peak at 2.1 Å. The CO$_2$RR activity of the synthesized catalyst is evaluated in various types of electrolyzer, demonstrating a CO faradaic efficiency exceeding 15% in a H-cell and 50% in a flow-cell, even in a phosphate buffer at pH 2. The introduction of K+ cations further elevates the catalyst's selectivity to 90% in the same pH environment. This catalyst development holds the potential to be a crucial advancement for designing an acidic reactor, enhancing carbon efficiency, and optimizing the performance of the CO$_2$ electrolyzer by preventing the penetration of produced anions through the membrane.