The full reaction network and the elementary steps are shown in Fig. and Table For the present model, we have chosen to restrict the reaction network model to the most wellstudied mechanistic pathways associated with Cu (100) surface. This surface is dominating in polycrystalline copper particles. At the same time, we acknowledge that under specific reaction context (temperature, fluids composition, electrode potential, support material and nanoparticle size) there exist certain distribution of facets on an active catalyst. While there is a continuing debate on mechanistic pathways on different Cu surfaces, the extension of the model to the distribution of facets and a more complex model of a distribution of reaction networks is beyond the scope of this work. The use of nanostructured catalysts results in different roughness factors (RFs), which represent the ratio of the electrochemical active surface area (ECSA) to the geometric electrode area (GESA). In this work, we looked at the increased number of sites as it pertains to GDEs rather than the intrinsic catalytic activity (average turnover frequency). Therefore, nanocatalysts with different roughness factors (surface areas) will achieve mass transport limitations at different rates. The surface area of a GDE is directly linked with its surface pH (local pH) of the porous catalytic bed due to the increased production of OH -ions from increased active sites.