Nanoconfinement Allows a Less Active Cascade Catalyst to Produce More C2+ Products in Electrochemical CO2 Reduction

Enzymes with multiple distinct active sites linked by substrate channels combined with control over the solution environment near the active sites enable the formation of complex products from simple reactants via the confinement of intermediates. We mimic this concept to facilitate the electrochemical carbon dioxide reduction reaction using nanoparticles with a core that produces intermediate CO at different rates and a porous copper shell. CO2 reacts at the core to produce CO which then diffuses through the Cu to give higher order hydrocarbon molecules. By altering the rate of CO2 delivery, the activity of the CO producing site, and the applied potential, we show that the nanoparticle with lower activity for CO formation produces greater amounts of hydrocarbon products. This is attributed to a combination of higher local pH and the lower amount of CO, resulting in more stable nanoparticles. However, when lower amounts of CO2 were delivered to the core, the particles that are more active for CO formation produce more C3 products. The importance of these results is twofold. They show that in cascade reactions, more active intermediate producing catalysts do not necessarily give greater amounts of high-value products. The effect an intermediate producing active site has on the local solution environment around the secondary active site plays an important role. As the less active catalyst for producing CO also possesses greater stability, we show that nanoconfinement can be used to get the best of both worlds with regard to having a stable catalyst with high activity.This research was financially supported by the Australian Research Council Discovery Projects (DP210102698 to J.J.G. and DP190102659 to R.D.T.) and the Mark Wainwright Analytical Centre (MWAC) at UNSW. This work used the facilities supported by Microscopy Australia at the Electron Microscope Unit at UNSW. S.V.S. and P.B.O'M. acknowledge the Australian Government Research Training Program Scholarship for financial support. W.S. acknowledges the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program [CasCat (833408)]