Low-cost renewable electricity has raised the prospect of using electrochemistry to synthesize fuels and chemicals. CO electrolysis can be used to make valuable multi-carbon products, but previous systems have shown low CO conversion and dilute product streams. Here we describe CO gas diffusion electrolysis cells that make concentrated products at high rates and modest voltages, including a cell that directly outputs a >1 M acetate solution. Our results reveal critical design features for maximizing the efficiency of C 2 electrosynthesis.

A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown. The relative phase stabilities for these products are dependent upon the reactant mole fractions in the initial reaction gel. This phase stability information was used to direct the synthesis of two new noncentrosymmetric compounds, using either (S)-(-)-3-aminoquinuclidine dihydrochloride or (R)-(+)-3-aminoquinuclidine dihydrochloride. [(R)-C7H16N2]2[Mo8O26] and [(S)-C7H16N2]2[Mo8O26] both crystallize in the noncentrosymmetric space group P2(1) (No. 4), which has the polar crystal class 2 (C2). The second-harmonic generation activities were measured on sieved powders. The structure-directing properties of the molybdate components in each compound were determined using bond valence sums. The structures of all five compounds were determined using single-crystal X-ray diffraction.

In the calculation of the vol% ethylene values in the main text, the volumetric rate of CO consumed for ethylene production was inadvertently used as the volumetric rate of C 2 H 4 production without including the 1 / 2 conversion factor. The corrected values are as follows.