(702f) Investigation of Liquid Fuel Generation from Carbon Dioxide over Bimetallic Systems

Electrochemical CO₂ reduction reaction (CO₂RR) to easy-to-store and -transport products, especially sustainable liquid fuels (C₃₊, i.e., propanol (C₃), butanol (C₄), and pentanol (C₅)) using renewable electricity represents a net zero-carbon path. However, currently, the catalyst design for CO₂RR-to-C₃₊ is very limited because (1) no pure metal catalyst could energy-efficiently convert CO₂to C₃₊ fuels; (2) the reaction mechanism is unknown.

According to previous work about long-chain hydrocarbons formation,¹ the alloy system with palladium and gold presents excellent catalysis performance for C₃-C₅ products with CO₂RR. We then designed a PdAu bimetallic catalyst (Figure 1a) as a study case and explored the mechanism of CO₂RR-to-C₃₊ via a combination of machine learning, density functional theory (DFT) and microkinetic modeling.³ In particular, our results show that C_n-C­H₂ coupling is more energetically favorable than C_n-CO. This further confirmed our hypothesis that to generate C₃₊ fuels, the reaction mechanism is a Ficher-Tropsch-like synthesis which passes by the key intermediate CH₂. The reaction energetics could be further promoted at the Pd-Au interfacial site as compared to the pure Pd or Au sites. For the future work, we will design a deep active learning algorithm to auto-generate and auto-select bimetallic interface sites for CO₂RR to long-chain hydrocarbon fuel generation. This theoretical research provides an innovative reaction mechanism, i.e., CH₂ insertion, for bimetallic system based CO₂RR to long-chain hydrocarbons (C₃₊). This work would further integrate energy storage of renewable electricity with the grid, enable storage for intermittent power, and would advance goals of net-zero carbon fuels.