Co‐Electrolysis of CO 2 and H 2 O to Syngas on Bimetallic Pd x Cu 1‐ x Catalysts for Tandem Thermochemical Conversion to Carbon Nanofibers

ABSTRACT Electrification of chemical production using renewable energy and abundant feedstocks offers a promising pathway for decarbonizing the chemical industry. Current efforts on CO 2 valorization largely focus on making chemicals and fuels. To help achieve net‐negative emissions through long‐term carbon storage, this study aims to develop efficient electrocatalysts for a tandem electrochemical‐thermochemical process to convert CO 2 into carbon nanofibers (CNFs). CO 2 and water are first electrochemically reduced in a membrane electrode assembly (MEA) electrolyzer to produce syngas (CO + H 2 ), which is subsequently fed into a thermochemical packed bed reactor to facilitate CNF growth. This work systematically evaluated Pd x Cu 1‐x bimetallic electrocatalysts to assess the effect of Pd–Cu alloying on enhancing syngas production while reducing Pd loading. Transmission electron microscopy and Raman spectroscopy confirmed the formation of high‐purity, crystalline CNFs, regardless of the syngas composition from the MEA. In situ X‐ray absorption spectroscopy and X‐ray diffraction measurements revealed that increasing Cu content in the Pd x Cu 1‐x alloy progressively inhibited palladium hydride formation, consistent with DFT calculations on the stability of Pd x Cu 1‐x under reducing electrochemical potentials.