The electroreduction of carbon dioxide (CO2RR) to CH4 stands as one of the promising paths for resourceful CO2 utilization in meeting the imminent “carbon‐neutral” goal of the near future. Yet, limited success has been witnessed in the development of high‐efficiency catalysts imparting satisfactory methane selectivity at a commercially viable current density. Herein, a unique category of CO2RR catalysts is fabricated with the yolk–shell nanocell structure, comprising an Ag core and a Cu2O shell that resembles the tandem nanoreactor. By fixing the Ag core and tuning the Cu2O envelope size, the CO flux arriving at the oxide‐derived Cu shell can be regulated, which further modulates the *CO coverage and *H adsorption at the Cu surface, consequently steering the CO2RR pathway. Density functional theory simulations show that lower CO coverage favors methane formation via stabilizing the intermediate *CHO. As a result, the best catalyst in the flow cell shows a high CH4 Faraday efficiency of 74 ± 2% and partial current density of 178 ± 5 mA cm−2 at −1.2 VRHE, ranking above the state‐of‐the‐art catalysts reported today for methane production. These findings mark the significance of precision synthesis in tailoring the catalyst geometry for achieving desired CO2RR performance.
Electrocatalytic reduction of CO2 into alcohols of high economic value offers a promising route to realize resourceful CO2 utilization. In this study, we choose three model bicentric copper complexes based on the expanded and fluorinated porphyrin structure, but different spatial and coordination geometry, to unravel their structure-property-performance correlation in catalyzing electrochemical CO2 reduction reactions. We show that the complexes with higher intramolecular tension and coordination asymmetry manifests a lower electrochemical stability and thus more active Cu centers, which can be reduced during electrolysis to form Cu clusters accompanied by partially-reduced or fragmented ligands. We demonstrate the hybrid structure of Cu cluster and partially reduced O-containing hexaphyrin ligand is highly potent in converting CO2 into alcohols, up to 32.5% ethanol and 18.3% n-propanol in Faradaic efficiencies that have been rarely reported. More importantly, we uncover an interplay between the inorganic and organic phases to synergistically produce alcohols, of which the intermediates are stabilized by a confined space to afford extra O-Cu bonding. This study underlines the exploitation of structure-dependent electrochemical property to steer the CO2 reduction pathway, as well as a potential generic tactic to target alcohol synthesis by constructing organic/inorganic Cu hybrids.
Electrochemical CO2 reduction (CO2RR) in a product-orientated and energy-efficient manner relies on rational catalyst design guided by mechanistic understandings. In this study, the effect of conducting support on the CO2RR behaviors of semi-conductive metal-organic framework (MOF) — Cu3(HITP)2 are carefully investigated. Compared to the stand-alone MOF, adding Ketjen Black greatly promotes C2H4 production with a stabilized Faradaic efficiency between 60-70% in a wide potential range and prolonged period. Multicrystalline Cu nano-crystallites in the reconstructed MOF are induced and stabilized by the conducting support via current shock and charge delocalization, which is analogous to the mechanism of dendrite prevention through conductive scaffolds in metal ion batteries. Density functional theory calculations elucidate that the contained multi-facets and rich grain boundaries promote C–C coupling while suppressing HER. This study underlines the key role of substrate-catalyst interaction, and the regulation of Cu crystalline states via conditioning the charge transport, in steering the CO2RR pathway.
Utilization of microbes as the carbon source and structural template to fabricate porous carbon has incentivized great interests owing to their diverse micromorphology and intricate intracellular structure, apart from the obvious benefit of “turning waste into wealth.” Challenges remain to preserve the biological structure through the harsh and laborious post‐synthetic treatments, and tailor the functionality as desired. Herein, Escherichia coli is directly coated with metal–organic frameworks (MOFs) through in situ assembly to fabricate N, P co‐doped porous carbon capsules expressing self‐phosphorized metal phosphides. While the MOF coating serves as an armoring layer for facilitating the morphology inheritance from the bio‐templates and provides metal sources for generating extra porosity and electrochemically active sites, the P‐rich phospholipids and N‐rich proteins from the plasma membrane enable carbon matrix doping and further yield metal phosphides. These unique structural and compositional features endow the carbon capsules with great capabilities in suppressing polysulfide shuttling and catalyzing reversible oxygen conversion, ultimately leading to the superb performance of lithium–sulfur batteries and zinc–air batteries. Combining the bio‐templating strategy with hierarchical MOF assembly, this work opens a new avenue for the fabrication of highly porous and functional carbon for advanced energy applications.
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