CO2 electrolysis is a key step in CO2 conversion into fuels and chemicals as a way of mitigating climate change. We report the synthesis and testing of a series of new anion‐conductive membranes (tradenamed Sustainion™) for use in CO2 electrolysis. These membranes incorporate the functional character of imidazolium‐based ionic liquids as co‐catalysts in CO2 reduction into a solid membrane with a styrene backbone. We find that the addition of an imidazolium group onto the styrene side‐chains increases the selectivity of the reaction from approximately 25 % to approximately 95 %. The current at 3 V is increased by a factor of 14. So far we have been able to tune these parameters to achieve stable cells that provide current densities higher than 100 mA cm−2 at 3 V cell potential with a CO product selectivity over 98 %. Stable performance was observed for 6 months of continuous operation (>150 000 000 turnovers). These results demonstrate that imidazolium polymers are ideal membranes for CO2 electrolysis.

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The recent development and market introduction of a new type of alkaline stable imidazole-based anion exchange membrane and related ionomers by Dioxide Materials is enabling the advancement of new and improved electrochemical processes which can operate at commercially viable operating voltages, current efficiencies, and current densities. These processes include the electrochemical conversion of CO2 to formic acid (HCOOH), CO2 to carbon monoxide (CO), and alkaline water electrolysis, generating hydrogen at high current densities at low voltages without the need for any precious metal electrocatalysts. The first process is the direct electrochemical generation of pure formic acid in a three-compartment cell configuration using the alkaline stable anion exchange membrane and a cation exchange membrane. The cell operates at a current density of 140 mA/cm2 at a cell voltage of 3.5 V. The power consumption for production of formic acid (FA) is about 4.3–4.7 kWh/kg of FA. The second process is the electrochemical conversion of CO2 to CO, a key focus product in the generation of renewable fuels and chemicals. The CO2 cell consists of a two-compartment design utilizing the alkaline stable anion exchange membrane to separate the anode and cathode compartments. A nanoparticle IrO2 catalyst on a GDE structure is used as the anode and a GDE utilizing a nanoparticle Ag/imidazolium-based ionomer catalyst combination is used as a cathode. The CO2 cell has been operated at current densities of 200 to 600 mA/cm2 at voltages of 3.0 to 3.2 respectively with CO2 to CO conversion selectivities of 95–99%. The third process is an alkaline water electrolysis cell process, where the alkaline stable anion exchange membrane allows stable cell operation in 1 M KOH electrolyte solutions at current densities of 1 A/cm2 at about 1.90 V. The cell has demonstrated operation for thousands of hours, showing a voltage increase in time of only 5 μV/h. The alkaline electrolysis technology does not require any precious metal catalysts as compared to polymer electrolyte membrane (PEM) design water electrolyzers. In this paper, we discuss the detailed technical aspects of these three technologies utilizing this unique anion exchange membrane.

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Colossal solar energy conversion and storage studies using photoelectrochemical cells (PECs) have been undertaken in the past four decades; however, how to efficiently utilize solar energy despite the intermittent nature of sunlight still remains a challenge. In this paper, a WO 3 /TiO 2 hybrid photoelectrode was coupled with our newly developed all-vanadium photoelectrochemical cell (PEC) with the aim of implementing photoelectrochemical solar energy conversion and storage. Zeroresistance ammetry (ZRA) and electrochemical impedance spectroscopy (EIS) were employed to study the photoelectrochemical response of this system in the conversion and storage of solar energy both under illumination and in the dark. The preliminary results proved the feasibility of this approach to store/release solar energy, even under dark conditions and showed that hydrogen tungsten bronze was responsible for the storage and release of photogenerated electrons from the semiconductor. The results also indicated an important synergy between electron storage and the all-vanadium electrolytes, which potentially offers great reversibility, high-capacity electron storage, and significant improvement in the photocurrent. To better understand the observed photoelectrochemical and electrochemical impedance behavior of our system, a model that unfolds the WO 3 electron storage mechanism and photogenerated charge carrier pathways in the all-vanadium PEC is proposed.

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