Quantum Diagonalization–Aided Design and Validation of Catalytic Pathways for Multi-Carbon Products in Carbon Dioxide Electroreduction

This work presents an integrated approach that combines in-situ experimental analysis with quantum-accelerated reaction-pathway calculations to resolve the mechanisms governing C–C coupling and C2+ formation in electrochemical CO2 reduction. By employing a hybrid framework that couples density functional theory (DFT) with quantum diagonalization (SQD), we achieved faster and more accurate mapping of intermediate energetics compared to classical methods. The electrocatalyst design strategy focuses on defect engineering in mixed two-dimensional chalcogenides, where controlled chalcogen ratios yield dominant defect types that enhance surface dipoles, increase d-orbital availability near the Fermi level, and strengthen CO2 and *CO adsorption. Each of these steps is essential for lowering the coupling barrier. Guided by these quantum calculations, synthesized chalcogenides are probed via in-situ techniques such as Raman and SFG, supported by ex-situ XPS and high-resolution electron microscopy to quantify defect populations and adsorption behavior. Electrochemical CO2 reduction benchmarking is performed in RDE and flow-cell configurations to quantify reaction yield, HER suppression, and overall performance. This combined quantum calculation-experimental framework establishes a predictive methodology for rationally steering CO2RR toward multi-carbon products through defect-ratio engineering.