Copper nanoclusters derived from copper phthalocyanine as real active sites for CO2 electroreduction: Exploring size dependency on selectivity ‐ A mini review

Abstract

AbstractThe electrochemical reduction reaction of CO2 (CO2RR) holds promise for converting CO2 into valuable fuels and chemicals, particularly when powered by renewable electricity, thereby aiding in reducing atmospheric CO2 levels and addressing climate change. Copper phthalocyanine and its derivatives (Cu‐Pcs) have attracted significant attention as versatile electrocatalytic materials with high selectivity toward various hydrocarbon products. However, the real active sites of Cu‐Pcs for different products vary, and there is a lack of comprehensive summary. To address this gap, we analyze and summarize previous research, yielding the following insights: Cu‐Pcs undergo reconstruction and demetallization during CO2RR, with Cu(II) converting to Cu(0), forming transient copper nanoclusters (Cu NCs). The selectivity for CO2RR products closely correlates with the size of those derived Cu NCs. Specifically, reversible Cu NCs with ultrasmall sizes (≤2 nm), which revert to Cu‐Pcs after electrolysis, exhibit high selectivity toward CH4. As Cu NCs increase in size, there is a higher CO coverage, promoting CO generation. When Cu NCs exceed a critical threshold size (approximately 15 nm), C‐C coupling can occur, facilitating the formation of multicarbon (C2+) products. Furthermore, the structure of macrocycles, types of functional groups, and properties of carbon substrates influence the size and electron density of Cu NCs, thereby impacting the selectivity of CO2RR products.