Investigating CO Electrolysis on cobalt at elevated temperatures to produce C4+ hydrocarbons

Abstract

Defossilizing aviation and shipping industries require scalable, carbon-neutral routes to energy-dense liquid fuels. CO 2 electrolysis has emerged as a promising route to carbon-neutral fuels, but Cu-based catalysts are largely limited to producing short-chain (< C 3 ) products. In contrast, strong *CO-binding metals that underpin thermochemical Fischer-Tropsch (FT) catalysis remain largely unexplored under electrochemical conditions. Here, we investigate Co catalyst for producing C 4+ hydrocarbons in membrane electrode assembly (MEA) reactors operated at elevated temperatures (30 -80 °C) and industrially relevant current densities. At 80 °C and 250 mA/cm 2 , Co produces a complex spectrum of 28 distinct C₁ -C₆ + products, with hydrocarbon partial current densities increasing linearly with temperature. Density functional theory calculations reveal that direct *CO dissociation on Co remains kinetically inaccessible under these reaction conditions, pointing instead to protonation-mediated pathways in C-C bond formation. Strong adsorption of unsaturated hydrocarbons leads to surface coking and progressive deactivation, which is mitigated through pulsed electrolysis. Unlike Cu, the activity and selectivity trends on Co are only weakly dependent on alkali-metal cation identity, highlighting a mechanistic regime more closely analogous to FT catalysis than to classical *CO-*CO dimerization. Together, these findings establish Co as a prototype strong *CO-binding catalyst for electrochemical long-chain hydrocarbon synthesis and provide mechanistic design principles for developing high-temperature electrochemical routes to sustainable, naphtha-range fuels.