Reported here is the chelate effect as a design principle for tuning heterogeneous catalysts for electrochemical CO₂ reduction. Palladium functionalized with a chelating tris-N-heterocyclic carbene (NHC) ligand (Pd-timtmb^Me ) exhibits a 32-fold increase in activity for electrochemical reduction of CO₂ to C1 products with high Faradaic efficiency (FE_C1 =86 %) compared to the parent unfunctionalized Pd foil (FE=23 %), and with sustained activity relative to a monodentate NHC-ligated Pd electrode (Pd-mimtmb^Me ). The results highlight the contributions of the chelate effect for tailoring and maintaining reactivity at molecular-materials interfaces enabled by surface organometallic chemistry.

Conversion of carbon monoxide (CO), a major one-carbon product of carbon dioxide (CO₂) reduction, into value-added multicarbon species is a challenge to addressing global energy demands and climate change. Here we report a modular synthetic approach for aqueous electrochemical CO reduction to carbon-carbon coupled products via self-assembly of supramolecular cages at molecular-materials interfaces. Heterobimetallic cavities formed by face-to-face coordination of thiol-terminated metalloporphyrins to copper electrodes through varying organic struts convert CO to C2 products with high faradaic efficiency (FE = 83% total with 57% to ethanol) and current density (1.34 mA/cm²) at a potential of -0.40 V vs RHE. The cage-functionalized electrodes offer an order of magnitude improvement in both selectivity and activity for electrocatalytic carbon fixation compared to parent copper surfaces or copper functionalized with porphyrins in an edge-on orientation.

Conversion of the greenhouse gas carbon dioxide (CO2) to value-added products is an important challenge for sustainable energy research, and nanomaterials offer a broad class of heterogeneous catalysts for such transformations. Here we report a molecular surface functionalization approach to tuning gold nanoparticle (Au NP) electrocatalysts for reduction of CO2 to CO. The N-heterocyclic (NHC) carbene-functionalized Au NP catalyst exhibits improved faradaic efficiency (FE = 83%) for reduction of CO2 to CO in water at neutral pH at an overpotential of 0.46 V with a 7.6-fold increase in current density compared to that of the parent Au NP (FE = 53%). Tafel plots of the NHC carbene-functionalized Au NP (72 mV/decade) vs parent Au NP (138 mV/decade) systems further show that the molecular ligand influences mechanistic pathways for CO2 reduction. The results establish molecular surface functionalization as a complementary approach to size, shape, composition, and defect control for nanoparticle catalyst design.

The water-gas shift (WGS) reaction (where carbon monoxide plus water yields dihydrogen and carbon dioxide) is an essential process for hydrogen generation and carbon monoxide removal in various energy-related chemical operations. This equilibrium-limited reaction is favored at a low working temperature. Potential application in fuel cells also requires a WGS catalyst to be highly active, stable, and energy-efficient and to match the working temperature of on-site hydrogen generation and consumption units. We synthesized layered gold (Au) clusters on a molybdenum carbide (α-MoC) substrate to create an interfacial catalyst system for the ultralow-temperature WGS reaction. Water was activated over α-MoC at 303 kelvin, whereas carbon monoxide adsorbed on adjacent Au sites was apt to react with surface hydroxyl groups formed from water splitting, leading to a high WGS activity at low temperatures.