For multi-step kinetics, the Tafel slope, or related the transfer coefficient ac,j, has been used to infer which elementary step is rate-limiting in the formation of a particular reaction product. A commonly used method to calculate Tafel slopes involves a least-squares regression on the linear portion of the logarithm of the measured current density vs cathode voltage (i.e., the kinetic region) excluding data that lie in the mass-transport limited regime (Figure , top). For the electrochemical reduction of CO2, the mass-transport-limited regime occurs at potentials for which the predicted rate of CO2 consumption by electrochemical and homogeneous chemical reactions becomes greater than the rate of CO2 transport to the surface. Mass-transport limitations in CO2R are caused primarily by the low solubility and diffusion coefficient of CO2 in the aqueous electrolyte. Because the regimes of kinetic control and the onset of mass-transfer control are defined arbitrarily, this method of identifying the regime of kinetic control is prone to human error and leads to a reduction in the number of data points available for analysis. It is also notable that in electrochemical synthesis the product must be quantified at every applied potential through time-consuming steady-state measurements. The need for product quantification contrasts with water electrolysis for which catalytic behavior can be measured rapidly at thousands of points via linear-sweep voltammetry. Because data in electrochemical synthesis must be collected by steady-state chronopotentiometry or chronoamperometry to generate sufficient product for quantification, rapid current-voltage sweeps are impractical if one wants to determine the partial current densities for each product. In other words, the steady-state nature of electrochemical synthesis, in which multiple products are formed, limits the number of available data points for each product. Prior work has sought to address these concerns and provide rigorous methods for determining kinetic parameters. as well as the complex dependences of the intrinsic kinetics on species activities that affect observed kinetics. In this work, we present a one-dimensional, reaction-transport model of the electrochemical reduction of CO2 to CO and H2 over an Ag catalyst that is then used in combination with advanced data-analysis tools to fit the Tafel parameters (i.e., ac and i0) for a variety of Ag catalysts. This approach provides a rigorous means for identifying the parameters required for continuum simulations. Application of this approach to 21 data sets for CO2 reduction to CO on Ag in similar experimental setups reveals that the fitted rate parameters are broadly distributed, probably due to differences in catalyst morphology (i.e., distribution of surface facets and roughness). The methodology reported here provides a rigorous approach for determining the Tafel parameters associated with product partial current densities vs cathodic potential curves obtained for electrochemical processes that produce multiple products. This finding is particularly important for systems in which the formation of one product influences the rate of formation of other products through the effects of mass transfer and bulk reactions. chosen to coincide with that used in the experimental data set to be fitted, and the thickness of the associated mass-transport boundary layer (𝐿 () ) is fit along with the kinetic parameters. We note further that all of the experimental data examined in this study were acquired using a flow cell (i.e., an H-cell) with well-defined hydrodynamics and a reference electrode located in the potassium bicarbonate electrolyte (Figure ). The decision to consider only Ag catalysts used under similar experimental conditions limits the amount of available data in literature, but enables deconvolution of the catalytic behavior from other variables. We note that previous work has shown that a 1-D representation is capable of capturing the requisite concentration and potential gradients needed to model aqueous CO2 reduction on planar catalysts. The CO and H2 evolution reactions (COER and HER) occur at the surface of the Ag electrode, with the following stoichiometries and standard potentials.