Bimetallic Metal Sites in Metal-Organic Frameworks Facilitate the Production of 1-Butene from Electrosynthesized Ethylene.

Converting CO to synthetic hydrocarbon fuels is of increasing interest. In light of progress in electrified CO to ethylene, we explored routes to dimerize to 1-butene, an olefin that can serve as a building block to ethylene longer-chain alkanes. With goal of selective and active dimerization, we investigate a series of metal-organic frameworks having bimetallic catalytic sites.

In situ copper faceting enables efficient CO/CO electrolysis.

The copper (Cu)-catalyzed electrochemical CO reduction provides a route for the synthesis of multicarbon (C) products. However, the thermodynamically favorable Cu surface (i.e.

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.

Surface hydroxide promotes CO electrolysis to ethylene in acidic conditions.

Performing CO reduction in acidic conditions enables high single-pass CO conversion efficiency. However, a faster kinetics of the hydrogen evolution reaction compared to CO reduction limits the selectivity toward multicarbon products. Prior studies have shown that adsorbed hydroxide on the Cu surface promotes CO reduction in neutral and alkaline conditions.

Constrained C adsorbate orientation enables CO-to-acetate electroreduction.

The carbon dioxide and carbon monoxide electroreduction reactions, when powered using low-carbon electricity, offer pathways to the decarbonization of chemical manufacture. Copper (Cu) is relied on today for carbon-carbon coupling, in which it produces mixtures of more than ten C chemicals: a long-standing challenge lies in achieving selectivity to a single principal C product. Acetate is one such C compound on the path to the large but fossil-derived acetic acid market.

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.

Coordination Polymer Electrocatalysts Enable Efficient CO-to-Acetate Conversion.

Upgrading carbon dioxide/monoxide to multi-carbon C products using renewable electricity offers one route to more sustainable fuel and chemical production. One of the most appealing products is acetate, the profitable electrosynthesis of which demands a catalyst with higher efficiency. Here, a coordination polymer (CP) catalyst is reported that consists of Cu(I) and benzimidazole units linked via Cu(I)-imidazole coordination bonds, which enables selective reduction of CO to acetate with a 61% Faradaic efficiency at -0.

Strain in Copper/Ceria Heterostructure Promotes Electrosynthesis of Multicarbon Products.

Elastic strains in metallic catalysts induce enhanced selectivity for carbon dioxide reduction (COR) toward valuable multicarbon (C) products. However, under working conditions, the structure of catalysts inevitably undergoes reconstruction, hardly retaining the initial strain. Herein, we present a metal/metal oxide synthetic strategy to introduce and maintain the tensile strain in a copper/ceria heterostructure, enabled by the presence of a thin interface layer of CuO/CeO.

High-Rate and Selective CO Electrolysis to Ethylene via Metal-Organic-Framework-Augmented CO Availability.

High-rate conversion of carbon dioxide (CO ) to ethylene (C H ) in the CO reduction reaction (CO RR) requires fine control over the phase boundary of the gas diffusion electrode (GDE) to overcome the limit of CO solubility in aqueous electrolytes. Here, a metal-organic framework (MOF)-functionalized GDE design is presented, based on a catalysts:MOFs:hydrophobic substrate materials layered architecture, that leads to high-rate and selective C H production in flow cells and membrane electrode assembly (MEA) electrolyzers. It is found that using electroanalysis and operando X-ray absorption spectroscopy (XAS), MOF-induced organic layers in GDEs augment the local CO concentration near the active sites of the Cu catalysts.

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.

Boride-derived oxygen-evolution catalysts.

Metal borides/borates have been considered promising as oxygen evolution reaction catalysts; however, to date, there is a dearth of evidence of long-term stability at practical current densities. Here we report a phase composition modulation approach to fabricate effective borides/borates-based catalysts. We find that metal borides in-situ formed metal borates are responsible for their high activity.

Ternary Alloys Enable Efficient Production of Methoxylated Chemicals via Selective Electrocatalytic Hydrogenation of Lignin Monomers.

We explore the selective electrocatalytic hydrogenation of lignin monomers to methoxylated chemicals, of particular interest, when powered by renewable electricity. Prior studies, while advancing the field rapidly, have so far lacked the needed selectivity: when hydrogenating lignin-derived methoxylated monomers to methoxylated cyclohexanes, the desired methoxy group (-OCH) has also been reduced. The ternary PtRhAu electrocatalysts developed herein selectively hydrogenate lignin monomers to methoxylated cyclohexanes-molecules with uses in pharmaceutics.

Stable, active CO reduction to formate via redox-modulated stabilization of active sites.

Electrochemical reduction of CO (COR) to formic acid upgrades waste CO; however, up to now, chemical and structural changes to the electrocatalyst have often led to the deterioration of performance over time. Here, we find that alloying p-block elements with differing electronegativities modulates the redox potential of active sites and stabilizes them throughout extended COR operation. Active Sn-Bi/SnO surfaces formed in situ on homogeneously alloyed BiSn crystals stabilize the COR-to-formate pathway over 2400 h (100 days) of continuous operation at a current density of 100 mA cm.

Gold-in-copper at low *CO coverage enables efficient electromethanation of CO.

The renewable-electricity-powered CO electroreduction reaction provides a promising means to store intermittent renewable energy in the form of valuable chemicals and dispatchable fuels. Renewable methane produced using CO electroreduction attracts interest due to the established global distribution network; however, present-day efficiencies and activities remain below those required for practical application. Here we exploit the fact that the suppression of *CO dimerization and hydrogen evolution promotes methane selectivity: we reason that the introduction of Au in Cu favors *CO protonation vs.

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.

Silica-copper catalyst interfaces enable carbon-carbon coupling towards ethylene electrosynthesis.

Membrane electrode assembly (MEA) electrolyzers offer a means to scale up CO-to-ethylene electroconversion using renewable electricity and close the anthropogenic carbon cycle. To date, excessive CO coverage at the catalyst surface with limited active sites in MEA systems interferes with the carbon-carbon coupling reaction, diminishing ethylene production. With the aid of density functional theory calculations and spectroscopic analysis, here we report an oxide modulation strategy in which we introduce silica on Cu to create active Cu-SiO interface sites, decreasing the formation energies of OCOH* and OCCOH*-key intermediates along the pathway to ethylene formation.

Enhanced multi-carbon alcohol electroproduction from CO via modulated hydrogen adsorption.

Multi-carbon alcohols such as ethanol are valued as fuels in view of their high energy density and ready transport. Unfortunately, the selectivity toward alcohols in CO/CO electroreduction is diminished by ethylene production, especially when operating at high current densities (>100 mA cm). Here we report a metal doping approach to tune the adsorption of hydrogen at the copper surface and thereby promote alcohol production.

Chloride-mediated selective electrosynthesis of ethylene and propylene oxides at high current density.

Chemicals manufacturing consumes large amounts of energy and is responsible for a substantial portion of global carbon emissions. Electrochemical systems that produce the desired compounds by using renewable electricity offer a route to lower carbon emissions in the chemicals sector. Ethylene oxide is among the world's most abundantly produced commodity chemicals because of its importance in the plastics industry, notably for manufacturing polyesters and polyethylene terephthalates.

CO electrolysis to multicarbon products at activities greater than 1 A cm.

Electrolysis offers an attractive route to upgrade greenhouse gases such as carbon dioxide (CO) to valuable fuels and feedstocks; however, productivity is often limited by gas diffusion through a liquid electrolyte to the surface of the catalyst. Here, we present a catalyst:ionomer bulk heterojunction (CIBH) architecture that decouples gas, ion, and electron transport. The CIBH comprises a metal and a superfine ionomer layer with hydrophobic and hydrophilic functionalities that extend gas and ion transport from tens of nanometers to the micrometer scale.

Efficient Methane Electrosynthesis Enabled by Tuning Local CO Availability.

The electroreduction of carbon dioxide (CORR) to valuable chemicals is a promising avenue for the storage of intermittent renewable electricity. Renewable methane, obtained via CORR using renewable electricity as energy input, has the potential to serve as a carbon-neutral fuel or chemical feedstock, and it is of particular interest in view of the well-established infrastructure for its storage, distribution, and utilization. However, CORR to methane still suffers from low selectivity at commercially relevant current densities (>100 mA cm).