Dilute Alloy Electrocatalysts for Practical CO2 Electroreduction

Licentiate thesis, 2026

Electrochemical conversion of CO2 into fuels and value-added chemicals offers a compelling route to simultaneously address fossil fuel dependence and renewable energy intermittency. Copper is the only monometallic electrocatalyst capable of reducing CO2 to multi-carbon (C2+) products such as ethylene and ethanol, making it the central focus of efforts to develop practical CO2 electrolysis technologies. However, two fundamental challenges limit progress: the difficulty of achieving and maintaining high C2+ selectivity on Cu-based catalysts, and the lack of in-depth studies conducted under industrially relevant operating conditions at high current densities. Dilute alloying, which is the incorporation of trace amounts of a secondary metal into the Cu host lattice, has emerged as a promising strategy to modify Cu surface reactivity and its C-C coupling capability. Yet, the influence of preparation method on the atomic-scale structure of dilute alloy nanoparticles, and how that structure governs electrocatalytic performance, remains poorly understood. In this thesis, the effect of Cu-Pd dilute alloy composition and synthesis route was investigated. It was shown that they jointly govern the structure and CO2 electroreduction performance of Cu-Pd dilute alloy nanoparticles in zero-gap electrolyzers at industrially relevant current densities. Cu-Pd dilute alloy nanoparticles with controlled Pd compositions were prepared by two wet-chemical routes; sequential reduction and co-reduction, and tested at high current densities in zero-gap electrolyzers.

The results demonstrate that dilute Pd alloying functions as a stability promoter under high-rate operating conditions, suppressing the current-density-dependent surge in hydrogen evolution that afflicts pure Cu and preserving faradaic efficiency toward CO2 reduction products. Furthermore, sequential reduction may preferentially produce Cu-Pd alloys with isolated surface Pd sites which outperform Cu-Pd alloys prepared via co-reduction at equivalent bulk composition. Together, these findings demonstrate that composition and synthesis routes must be jointly optimized to provide transferable design principles for robust and selective Cu-based electrocatalysts for practical CO2 electroreduction systems.