Electrical Double Layers Shape the Kinetics of Heterogeneous Thermochemical Catalysis

Growing evidence shows that heterogeneous thermochemical redox reactions can proceed through coupled electrochemical half-reactions at a mixed potential. Yet how the electrical double layer (EDL), which sets the local reaction environment, regulates these reactions remains poorly understood, especially on supported catalysts where neighboring double layers can overlap. Here we develop a minimal Au–Pd model coupling Poisson–Boltzmann electrostatics to Frumkin-corrected Butler–Volmer kinetics, with anion oxidation on Au and cation reduction on Pd. First, we show that the EDL itself cannot be neglected: for Au and Pd electronically connected but spatially separated, so that their double layers do not overlap, resolving the EDL substantially changes the predicted kinetics relative to an EDL-absent description. Second, comparing a physical mixture, a carbon-supported Janus configuration, and alternating Au–Pd stripes reveals distinct rates arising from EDL overlap. The effects of EDL on the mixed potential and mixed current are consolidated into an analytical expression. These results establish the EDL and its overlap as key, tunable factor linking catalyst structure to the kinetics of heterogeneous thermochemical reactions.