Linking electrocatalytic turnover to elementary step rates in hydrocarbon fuel oxidation.

Maximizing steady-state turnover rates is a central goal in electrocatalysis research, but improving one reaction step often impedes others. Navigating these trade-offs requires methods that systematically reveal how a single parameter change affects all key steps of a reaction mechanism. Here, we use electrochemical mass spectrometry to determine the potential-dependent rates of each principal step in propane oxidation on Pt and directly relate them to the steady-state turnover rate. Our analysis reveals that low steady-state activity arises from a mismatch between the optimal potentials for adsorption, conversion, and *CO oxidation. By applying alternating potentials to individually optimize adsorption and oxidation, we overcome this limitation and achieve rates exceeding those under constant-potential operation. This step-resolved approach clarifies how individual processes interact to govern overall activity and provides a framework for the rational design of electrocatalysts carrying out complex reactions at steady-state.