Acid-Stable Cu Cluster Precatalysts Enable High Energy and Carbon Efficiency in CO Electroreduction.

The electrochemical reduction of CO in acidic media offers the advantage of high carbon utilization, but achieving high selectivity to C products at a low overpotential remains a challenge. We identified the chemical instability of oxide-derived Cu catalysts as a reason that advances in neutral/alkaline electrolysis do not translate to acidic conditions. In acid, Cu ions leach from Cu oxides, leading to the deactivation of the C-active sites of Cu nanoparticles.

CO Electrolyzers.

CO electrolyzers have progressed rapidly in energy efficiency and catalyst selectivity toward valuable chemical feedstocks and fuels, such as syngas, ethylene, ethanol, and methane. However, each component within these complex systems influences the overall performance, and the further advances needed to realize commercialization will require an approach that considers the whole process, with the electrochemical cell at the center. Beyond the cell boundaries, the electrolyzer must integrate with upstream CO feeds and downstream separation processes in a way that minimizes overall product energy intensity and presents viable use cases.

Selective Electrified Propylene-to-Propylene Glycol Oxidation on Activated Rh-Doped Pd.

Renewable-energy-powered electrosynthesis has the potential to contribute to decarbonizing the production of propylene glycol, a chemical that is used currently in the manufacture of polyesters and antifreeze and has a high carbon intensity. Unfortunately, to date, the electrooxidation of propylene under ambient conditions has suffered from a wide product distribution, leading to a low faradic efficiency toward the desired propylene glycol. We undertook mechanistic investigations and found that the reconstruction of Pd to PdO occurs, followed by hydroxide formation under anodic bias.

Efficient multicarbon formation in acidic CO reduction via tandem electrocatalysis.

The electrochemical reduction of CO in acidic conditions enables high single-pass carbon efficiency. However, the competing hydrogen evolution reaction reduces selectivity in the electrochemical reduction of CO, a reaction in which the formation of CO, and its ensuing coupling, are each essential to achieving multicarbon (C) product formation. These two reactions rely on distinct catalyst properties that are difficult to achieve in a single catalyst.

Pressure dependence in aqueous-based electrochemical CO reduction.

Electrochemical CO reduction (COR) is an approach to closing the carbon cycle for chemical synthesis. To date, the field has focused on the electrolysis of ambient pressure CO. However, industrial CO is pressurized-in capture, transport and storage-and is often in dissolved form.

Doping Shortens the Metal/Metal Distance and Promotes OH Coverage in Non-Noble Acidic Oxygen Evolution Reaction Catalysts.

Acidic water electrolysis enables the production of hydrogen for use as a chemical and as a fuel. The acidic environment hinders water electrolysis on non-noble catalysts, a result of the sluggish kinetics associated with the adsorbate evolution mechanism, reliant as it is on four concerted proton-electron transfer steps. Enabling a faster mechanism with non-noble catalysts will help to further advance acidic water electrolysis.

Strong-Proton-Adsorption Co-Based Electrocatalysts Achieve Active and Stable Neutral Seawater Splitting.

Direct electrolysis of pH-neutral seawater to generate hydrogen is an attractive approach for storing renewable energy. However, due to the anodic competition between the chlorine evolution and the oxygen evolution reaction (OER), direct seawater splitting suffers from a low current density and limited operating stability. Exploration of catalysts enabling an OER overpotential below the hypochlorite formation overpotential (≈490 mV) is critical to suppress the chloride evolution and facilitate seawater splitting.

Bipolar membrane electrolyzers enable high single-pass CO electroreduction to multicarbon products.

In alkaline and neutral MEA CO electrolyzers, CO rapidly converts to (bi)carbonate, imposing a significant energy penalty arising from separating CO from the anode gas outlets. Here we report a CO electrolyzer uses a bipolar membrane (BPM) to convert (bi)carbonate back to CO, preventing crossover; and that surpasses the single-pass utilization (SPU) limit (25% for multi-carbon products, C) suffered by previous neutral-media electrolyzers. We employ a stationary unbuffered catholyte layer between BPM and cathode to promote C products while ensuring that (bi)carbonate is converted back, in situ, to CO near the cathode.

Eliminating the need for anodic gas separation in CO electroreduction systems via liquid-to-liquid anodic upgrading.

Electrochemical reduction of CO to multi-carbon products (C), when powered using renewable electricity, offers a route to valuable chemicals and fuels. In conventional neutral-media CO-to-C devices, as much as 70% of input CO crosses the cell and mixes with oxygen produced at the anode. Recovering CO from this stream adds a significant energy penalty.

Concentrated Ethanol Electrosynthesis from CO via a Porous Hydrophobic Adlayer.

Electrochemical CO reduction can convert waste emissions into dense liquid fuels compatible with existing energy infrastructure. High-rate electrocatalytic conversion of CO to ethanol has been achieved in membrane electrode assembly (MEA) electrolyzers; however, ethanol produced at the cathode is transported, via electroosmotic drag and diffusion, to the anode, where it is diluted and may be oxidized. The ethanol concentrations that result on both the cathodic and anodic sides are too low to justify the energetic and financial cost of downstream separation.

CO electrolysis to multicarbon products in strong acid.

Carbon dioxide electroreduction (COR) is being actively studied as a promising route to convert carbon emissions to valuable chemicals and fuels. However, the fraction of input CO that is productively reduced has typically been very low, <2% for multicarbon products; the balance reacts with hydroxide to form carbonate in both alkaline and neutral reactors. Acidic electrolytes would overcome this limitation, but hydrogen evolution has hitherto dominated under those conditions.

Low coordination number copper catalysts for electrochemical CO methanation in a membrane electrode assembly.

The electrochemical conversion of CO to methane provides a means to store intermittent renewable electricity in the form of a carbon-neutral hydrocarbon fuel that benefits from an established global distribution network. The stability and selectivity of reported approaches reside below technoeconomic-related requirements. Membrane electrode assembly-based reactors offer a known path to stability; however, highly alkaline conditions on the cathode favour C-C coupling and multi-carbon products.