CO2 Electrochemical Reduction Toward Acetate with Cu-based LDH Catalyst

This thesis investigated how cation composition and layer arrangement affect Cu-based electrodes for electrochemical CO2 reduction, with particular attention to acetate formation and competing hydrogen evolution. Two catalyst families were prepared on carbon paper: Cu/CuOx-MgAl layered electrodes with opposite deposition orders, and Cu-Mg-Al, Cu-Ca-Mg-Al and Cu-Ca-Al compositions. The materials were studied by XRD, SEM-EDX and electrochemical measurements. CO2 electroreduction was performed in an H-type cell containing 0.3 M KHCO3, and gas and liquid products were analyzed by GC and 1H NMR, respectively. The deposition order strongly influenced layer formation, morphology and electrochemical behavior. Depositing MgAl on Cu/CuOx favored LDH formation, whereas the reverse arrangement produced a mainly Cu-rich surface. However, neither layered architecture improved acetate selectivity compared with the Cu2O-Cu0 benchmark, and hydrogen evolution remained important. In the composition series, CuMgAl showed the clearest LDH-related structure, the highest electrochemical surface area among the three compositions studied in detail, the lowest hydrogen production and the strongest preference for acetate. Partial replacement of Mg with Ca retained acetate as the main liquid product but increased hydrogen formation. Complete replacement with Ca resulted in low Ca incorporation, no clear LDH-related reflection and stronger hydrogen evolution, while formate became the main liquid product. Overall, high current or a large electrochemical surface area alone did not predict CO2 reduction performance. Under the conditions studied, CuMgAl provided the most favorable combination of LDH formation, low hydrogen production and acetate formation.