Molecular-scale CO spillover on a dual-site electrocatalyst enhances methanol production from CO2 reduction

Abstract

Cobalt phthalocyanine (CoPc) is recognized for catalysing electrochemical CO₂ reduction into methanol at high Faradaic efficiency but is subject to deactivation. Cobalt tetraaminophthalocyanine (CoPc-NH₂) shows improved stability, but its methanol Faradaic efficiency is below 30%. This study addresses these limitations in selectivity, reactivity and stability by rationally designing a dual-site cascade catalyst. Here we quantify the local concentration of CO, a key intermediate of the reaction, near a working CoPc-NH₂ catalyst and show that co-loading nickel tetramethoxyphthalocyanine (NiPc-OCH₃) with CoPc-NH₂ on multiwalled carbon nanotubes increases the generation and local concentration of CO. This dual-site cascade catalyst exhibits substantially higher performance than the original single-site CoPc-NH₂/carbon nanotube catalyst, reaching a partial current density of 150 mA cm⁻² and a Faradaic efficiency of 50% for methanol production. Kinetic analysis and in situ sum-frequency generation vibrational spectroscopy attribute this notable performance improvement to molecular-scale CO spillover from NiPc-OCH₃ sites to methanol-active CoPc-NH₂ sites.