A manganese complex on a gas diffusion electrode for selective CO2 to CO reduction

Abstract

Manganese carbonyl complexes have been studied extensively in solution as low cost, selective electrocatalysts with a low overpotential for CO₂ reduction but experiments are typically at low current densities. In this work, we examined their application in a gas diffusion electrode (GDE) flow cell and achieved partial current densities for CO, j_CO of ∼14 mA cm⁻² (−0.98 V_RHE) with a Faradaic efficiency of >50%. Although we did observe a gradual decrease in activity for the [Mn(2,2′-bipyridine)(CO)₃Br]/MWCNT (Mnbpy) GDE with a near neutral electrolyte over a 5 h experiment, it still achieves a higher initial partial current density for CO at a lower overpotential than a Ag nanoparticle benchmark electrode. Promisingly, initial studies of the Mnbpy GDE in a zero-gap electrolyser using a reverse biased bipolar membrane (BPM) achieved FE for CO of 70% at 50 mA cm⁻², despite the acidic environment induced through directly contacting the membranes cation exchange layer. Overall this study demonstrates the potential of GDEs for CO₂ reduction based on a catalyst using earth abundant elements.