Boosting Tunable Syngas Formation via Electrochemical CO₂ Reduction on Cu/In₂O₃ Core/Shell Nanoparticles

In this work, monodisperse core/shell Cu/In₂O₃ nanoparticles (NPs) were developed to boost efficient and tunable syngas formation via electrochemical CO₂ reduction for the first time. The efficiency and composition of syngas production on the developed carbon-supported Cu/In₂O₃ catalysts are highly dependent on the In₂O₃ shell thickness (0.4-1.5 nm). As a result, a wide H₂/CO ratio (4/1 to 0.4/1) was achieved on the Cu/In₂O₃ catalysts by controlling the shell thickness and the applied potential (from -0.4 to -0.9 V vs reversible hydrogen electrode), with Faraday efficiency of syngas formation larger than 90%. Specifically, the best-performing Cu/In₂O₃ catalyst demonstrates remarkably large current densities under low overpotentials (4.6 and 12.7 mA/cm² at -0.6 and -0.9 V, respectively), which are competitive with most of the reported systems for syngas formation. Mechanistic discussion implicates that the synergistic effect between lattice compression and Cu doping in the In₂O₃ shell may enhance the binding of *COOH on the Cu/In₂O₃ NP surface, leading to the enhanced CO generation relative to Cu and In₂O₃ catalysts. This report demonstrates a new strategy to realize efficient and tunable syngas formation via rationally designed core/shell catalyst configuration.