Stability of In2O3 nanoparticles in PTFE-containing gas diffusion electrodes for CO2 electroreduction to formate
Tim Wissink, Rim C. J. van de Poll, Marta C. Figueiredo, Emiel J. M. Hensen
Abstract
Electrocatalytic conversion of CO 2 to fuels and chemicals can help mitigate climate change by reuse of the greenhouse gas. Formic acid is an interesting product of electrochemical CO 2 reduction, because it can serve as a liquid hydrogen carrier. Indium-based electrodes show promising activity and selectivity towards formic acid formation during CO 2 electroreduction. However, the low stability of such electrodes at high current density limits their implementation in industry. Herein, we optimize a gas diffusion electrode (GDE) containing ~6 nm In 2 O 3 nanoparticles obtained by flame spray pyrolysis. The catalyst exhibits high initial faradaic efficiency towards formate (> 80%) at current densities up to 200 mA/cm 2 . In situ Raman spectroscopy reveals that the In 2 O 3 particles rapidly reduce under reaction conditions, demonstrating that metallic indium is the active phase for CO 2 reduction. Degradation mechanisms of the catalyst during 50 h at high current density were studied using XPS, in situ Raman, TEM and SEM, and elemental analysis of the electrolyte. Catalyst reduction, sintering of the active phase and dissolution of indium could be excluded as a cause of the declining FE. Adding carbon and hydrophobic PTFE particles to the catalyst in the GDE improves CO 2 supply and prevents early saturation of the GDE by liquid electrolyte. The optimized GDE configuration inhibits hydrogen evolution and demonstrates increased stability during 50 h of CO 2 electroreduction.