Durable Solar-Powered Systems with Ni-Catalysts for Conversion of CO₂ or CO to CH₄

Abstract

Photocatalytic conversion of CO2 to reduced carbon states using sunlight and an earth-abundant catalyst could provide a critically needed source of renewable energy. Very few earth-abundant catalysts have shown CO2 to CH4 reactivity, and significant opportunities exist to improve catalyst durability. Through the strategic design of a novel, redox-active bipyridyl-N-heterocyclic carbene macrocyclic ligand complexed with nickel, CO2 is converted into the energy-rich solar fuel, CH4, photocatalytically with a photosensitizer in the presence of water. Up to 19 000 turnovers of CH4 from CO2 are observed. An exceptional turnover number of 570 000 for CH4 production via a photodriven formal hydrogenation of CO to CH4 was also found. This unique reactivity from a tunable, highly durable macrocyclic framework was studied via a series of photocatalytic and electrocatalytic reactions varying the atmospheric composition, as well as by isotopic labeling experiments and quantum yield calculations to evaluate the effect of ligand structure on product generation.

Electro‐ and Photochemical Reduction of CO2 by Molecular Manganese Catalysts: Exploring the Positional Effect of Second‐Sphere Hydrogen‐Bond Donors

“…The least active catalyst in the series was 3‐Mn , which performed worse than the parent complex. Additional studies with the best catalyst 1‐Mn demonstrate that lowering the catalyst concentration elevates the observed TONs for CO 2 reduction, presumably because deleterious bimolecular catalyst‐catalyst deactivation pathways are minimized as previously proposed [13b,30] . Very low catalyst concentrations may also provide insight into how site‐isolated surface‐bound photocatalysts will behave.…”

Secondary-Sphere Effects in Molecular Electrocatalytic CO2 Reduction

“…Bringing molecular design principles to materials seems to be another viable strategy for using secondary-sphere effects in electrocatalysis: Gong et al (2017) immobilized porphyrin cages on Cu electrodes to tune activity and selectivity for carbon–carbon coupling products from CO 2 reduction through supramolecular effects. Recent reports have also described photocatalysts which convert CO 2 to methane from molecular catalysts related to those described here, which is promising for developing eventual electrocatalytic behavior (Rao et al, 2017; Shirley et al, 2019).…”

Structural engineering of 3D hierarchical Cd0.8Zn0.2S for selective photocatalytic CO2 reduction

“…During the light-driven conversion of CO2, the main reduction products (CO, CH2O, CH3OH, or CH4) depend on a reverse competitive relationship between the hydrogenation and deoxygenation pathways [43][44][45]. The formation of intermediates and final products is affected not only by the complex substrate-CO2 molecule contact mechanism but also by the carrier transport capability [46,47].…”