Electroreduction of CO 2 (eCO 2 RR) is a potentially sustainable approach for carbon-based chemical production. Despite significant progress, performing eCO 2 RR economically at scale is challenging. Here we report meeting key technoeconomic benchmarks simultaneously through electrolyte engineering and process optimization. A systematic flow electrolysis studyperforming eCO 2 RR to CO on Ag nanoparticles as a function of electrolyte composition (cations, anions), electrolyte concentration, electrolyte flow rate, cathode catalyst loading, and CO 2 flow rate -resulted in partial current densities of 417 and 866 mA/cm 2 with faradaic efficiencies of 100 and 98 % at cell potentials of À 2.5 and À 3.0 V with full cell energy efficiencies of 53 and 43 %, and a conversion per pass of 17 and 36 %, respectively, when using a CsOH-based electrolyte. The cumulative insights of this study led to the formulation of system design rules for high rate, highly selective, and highly energy efficient eCO 2 RR to CO.[a] S.

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The electrochemical reduction of pressurized carbon dioxide at tin cathode is considered a very promising process for the production of formic acid. Here, the process was studied in an undivided cell with the aim of developing a simple theoretical model. First, a large series of polarization and electrolyses was performed in order to evaluate the kinetic of the process. According to the literature, experimental results can be described by a simple reaction mechanism, which involves the following key stages: (i) mass transfer of CO2 to the cathode; (i) its adsorption described by a Langmuir equation; (iii) the reduction of adsorbed CO2. A simple model was developed based on the cathodic conversion of pressurized CO2 to HCOOH and on its anodic oxidation. The theoretical model was in a good agreement with experimental results collected in this work and in previous ones and well described the effect of several operative parameters, including current density, pressure and kind of reactor.

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