Turning natural copper phthalocyanine into high-loading single-atom catalysts using an electrochemically-generated template and cationic substitution

Abstract

Phthalocyanine (PC) has a unique N₄-coordinated structure that offers an inherent advantage with respect to the accommodation of metal ions. This feature can help overcome the limitations of many single-atom electrocatalysts, i.e. low loading and poor stability. Here, we detail the development of a universal electrochemical template and a cationic substitution synthesis protocol for preparing various single-atom catalysts with high-loading (≌ 8.6 wt%) from commercial copper phthalocyanine (CuPC). Commercial CuPC is transformed into Cu NPs and vacant N₄-sites are created during applied potential cycling. The generated vacant N₄-sites, with strong negative charges, can take-up Pd²⁺ ions from a precursor solution to create single-atom catalysts with Pd high-loadings. The material’s structural transformation and cationic substitution mechanism were investigated by in situ X-ray absorption spectroscopy (XAS). We also demonstrate the viability of extending the proposed electrochemical template synthesis method to the development of other high-loading transition metal single-atom catalysts, e.g., Ni, Co, and Fe.