CO₂ Electroreduction to Formate at a Partial Current Density of 930 mA cm^-2 with InP Colloidal Quantum Dot Derived Catalysts

We report formate production via CO₂ electroreduction at a Faradaic efficiency (FE) of 93% and a partial current density of 930 mA cm^-2, an activity level of potential industrial interest based on prior techno-economic analyses. We devise a catalyst synthesized using InP colloidal quantum dots (CQDs): The capping ligand exchange introduces surface sulfur, and XPS reveals the generation, operando, of an active catalyst exhibiting sulfur-protected oxidized indium and indium metal. Surface indium metal sites adsorb and reduce CO₂ molecules, while sulfur sites cleave water and provide protons. The abundance of exposed surface indium sites per quantum dot enables the high formate productivity achieved at low catalyst loadings. The high conductivity of the layer of nanoparticles under negative potential sustains the large current densities.