Boron Subphthalocyanine Complexes for CO₂ Electroreduction: Molecular Design and Catalytic Insights

Abstract

This study presents molecular boron subphthalocyanine complexes precursors ((Cl-B-SubPc) 1 and (Cl-B-SubPc-OC12H23) 2), designed for efficient CO2 reduction. The resulting heterogeneous catalysts exhibit remarkable overall efficiencies of 98%, integrated into practical cell assemblies. Optimizations encompass not only catalyst design but also operational conditions, facilitating prolonged CO2 electrolysis across various current densities. Varied C1-, C2-, and C3- product yields are observed at different reductive potentials, with electrocatalysis experiments conducted up to 200 mA/cm2. Comparative electrochemical analyses across H-cell and zero-gap cell electrolyzers show the potential for industrial scale-up. Mechanistic elucidation with in-situ UV-vis spectroelectrochemistry, DFT calculations, and ESR spectroscopy exhibits the involvement of boron N-C sites, initiating radical formation, and uitilizing boron's Lewis acid behavior in CO2 capture, followed by proton-coupled electron transfer. Throughout, the study underscores the transformative potential of boron subphthalocyanine systems in advancing CO2 utilization technologies.