CO<sub>2</sub>-mediated porphyrin catalysis in reversible Li-CO<sub>2</sub> cells

Abstract

Li-CO2 cells provide exceptional benefit by storing considerable energy and achieving environmental carbon fixation. However, the sluggish kinetics of the Li-CO2 reaction and severe cell polarization with low efficiency must be addressed. Here, we show that the manganese phthalocyanine (MnPc) molecule, a porphyrin-based homogeneous catalyst, significantly reduces the overpotential (similar to 50 %) and improves Li-CO2 cell performance during prolonged cycling. The reversible Li-CO2 reaction pathway proceeding via a LixCO2 intermediate species and catalyzed by MnPc was examined by in situ characterization and first principles calculations. We reveal the structural changes occurring in the MnPc catalyst with metal-to-ligand charge transfer when the electrochemically reduced CO2*- radical intermediate is bound to the Mn center after discharge; consequently, the reverse reaction enables recharging. This study introduces a way to understand and design organometallic homogeneous catalysts involving CO2 mediation of environmental energy storage systems and carbon negative.