Efficient CO2-to-methanol electrocatalysis in acidic media via microenvironment-tuned cobalt phthalocyanine

Abstract

Electrosynthesis of value-added chemicals in strong acids can mitigate carbon loss and the operational cost of CO2 reduction reaction (CO2RR). However, molecular catalysis for CO2RR is typically conducted in neutral or alkaline environments. CO2RR in acidic media is challenged by the scarcity of catalyst candidates, competitive hydrogen evolution and slow product formation. Here we report a locally ionic yet simultaneously hydrophobic and aerophilic layered structure that modulates the microenvironment surrounding cobalt phthalocyanine (CoPc) molecular catalysts, enabling efficient, multielectron CO2RR in acidic media. Experiment and theoretical modelling reveal that the polarized electrostatic field arising from the cationic groups suppresses hydronium migration. Concurrently, the van der Waals forces between the reactant gas and alkyl groups improve local CO availability, combining to achieve a methanol partial current density of 132 mA cm−2 with 62% selectivity at a pH of ~1 and –1.37 VRHE for CoPc, exceeding previous reports on neutral or alkaline electrolytes. The improved CO coverage also enables the detection of *CHO and *CO intermediates from in situ spectroscopy. We validate our strategy on various molecules, which champion the efficient inhibition of hydrogen evolution and improved CO2RR partial current density in acidic media. CoPc-based layered structure with similar ionic, hydrophobic and aerophilic interfaces also yields comparable methanol productivity.