The ability to maintain high efficiencies while simultaneously tuning the selectivity of the electrochemical reduction of CO 2 (ERC) using low-cost electrodes has proven to be one of the greatest obstacles to the widespread commercialization of this technology. In this study, we electrodeposit dendritic copper−indium alloys of various compositions and investigate their catalytic activity toward the reduction of CO 2 . These electrocatalysts are increasingly dendritic with higher In fraction and, depending on composition, consist of mixed phases of Cu, In, and Cu−In intermetallic phases. ERC at these electrodes produces formate at high efficiencies (up to 62% with a 80 at% In alloy, −1 V) while also tuning the CO/H 2 ratio to achieve an ideal syngas composition with a 40 at% In alloy (−1 V). The observed product distribution as a function of alloy composition and applied potential is rationalized in terms of the relative adsorption strengths of CO and COOH intermediates at Cu and In sites and the distinct variation with applied potential induced by the differences in electronic structure. This study highlights the opportunities of using alloys to enhance control over the product distribution and suggests that suitable alloys could be promising catalysts for the inexpensive and efficient production of fuels.

The electrochemical reduction of CO2 provides an alternative carbon‐neutral path for renewable synthesis of fuels and value‐added chemicals. This work demonstrates that dendritic, bimetallic Cu–Bi electrocatalysts with nanometer‐sized grains are capable of formate generation with a high selectivity. Optimizing composition of electrocatalyst could achieve a faradic efficiency of 90 % at −0.8 to −0.9 VRHE, and a partial current of more than 2 mA cm−2. The combination of Cu with Bi enables modulation of the adsorption strength of intermediates. This leads to an increased selectivity and suppressed formation of spurious species, especially hydrogen and CO. Comparison of product distribution for Cu–In versus Cu–Bi indicated that Bi is essential to induce a favorable adsorption configuration of the intermediate species and to promote formate production.

Most industrial hydrogenators are of the dead end type where the gas is bubbled at the bottom of the apparatus, builds up a certain pressure on top of the oil, and is not recirculated. The hydrogen needed by the reaction comes partly from the fraction of the bubbles that is absorbed and partly from the gas space. It was found that sodium sulfite oxidation follows the same mixing pattern, i.e., the highest rate of oxidation always occurred in the upper half of the liquid and correlated strongly with the Reynolds number of the turbine. It is shoran that for Reynolds numbers above 600 the optimum impeller position is about two thirds the liquid height measured from the bottom of the vessel. Information is given regarding the variations in selectivity, isomerization and hydrogenation of oils when the speed, relative location and dimensions of the turbine are varied.