Calculation of the Tafel slope and reaction order of the oxygen\n evolution reaction between pH 12 and pH 14 for the adsorbate mechanism

Despite numerous experimental and theoretical studies devoted to the oxygen\nevolution reaction, the mechanism of the OER on transition metal oxides remains\ncontroversial. This is in part owed to the ambiguity of electrochemical\nparameters of the mechanism such as the Tafel slope and reaction orders. We\ntook the most commonly assumed adsorbate mechanism and calculated the Tafel\nslopes and reaction orders with respect to pH based on microkinetic analysis.\nWe demonstrate that number of possible Tafel slopes strongly depends on a\nnumber of preceding steps and surface coverage. Furthermore, the Tafel slope\nbecomes pH dependent when the coverage of intermediates changes with pH. These\ninsights complicate the identification of a rate-limiting step by a single\nTafel slope at a single pH. Yet, simulations of reaction orders complementary\nto Tafel slopes can solve some ambiguities to distinguish between possible\nrate-limiting steps. The most insightful information can be obtained from the\nlow overpotential region of the Tafel plot. The simulations in this work\nprovide clear guidelines to experimentalists for the identification of the\nlimiting steps in the adsorbate mechanism using the observed values of the\nTafel slope and reaction order in pH-dependent studies.\n