Nanomorphology-Enhanced Gas-Evolution Intensifies CO2 Reduction Electrochemistry

Abstract

Nanostructured CO2 reduction catalysts now achieve near-unity reaction selectivity at increasingly improved Tafel slopes and low overpotentials. With excellent surface reaction kinetics, these catalysts encounter CO2 mass transport limitations at current densities ca. 20 mA cm–2. We show here that – in addition to influencing reaction rates and local reactant concentration – the morphology of nanostructured electrodes enhances long-range CO2 transport via their influence on gas-evolution. Sharper needle morphologies can nucleate and release bubbles as small as 20 μm, leading to a 4-fold increase in the limiting current density compared to a nanoparticle-based catalyst alone. By extending this observation into a diffusion model that accounts for bubble-induced mass transport near the electrode’s surface, diffusive transport can be directly linked to current densities and operating conditions, identifying efficient routes to >100 mA cm–2 production. We further extend this model to study the influence of mas...