Carbonate and/or bicarbonate formation is a major challenge that limits the efficiency and durability of the electrochemical CO2 reduction reaction (CO2RR). Here we show that applying an external alternating magnetic field (AMF) creates a localized heating field around a magnetic catalyst that reduces the build-up of OH− and increases the solubility of (bi)carbonate species at the catalyst–electrolyte interface, thereby suppressing (bi)carbonate precipitation. Ferromagnetic confined CrMnNiZnPd and CrNiCuZnAg high-entropy alloys have been designed and synthesized via a nebulization-blast strategy. Under an AMF, the confined CrMnNiZnPd and CrNiCuZnAg exhibit superior CO2RR activity towards single-carbon and multicarbon products in KHCO3 electrolyte, respectively, compared with no AMF, with stable operation over 200 h. The improved performance and durability persist in alkaline KOH and non-buffered KCl electrolytes, demonstrating the generality of this strategy across different electrolytes. These results establish AMF-induced local heating as an effective strategy to regulate interfacial reaction microenvironments and suggest its potential for mitigating (bi)carbonate-related limitations in CO2 electroreduction. Carbonate precipitation at the cathode caused by local alkalinity during electrocatalytic CO2 reduction represents a major limitation to carbon efficiency and system durability. Now local heating induced in ferromagnetic high-entropy alloys by an alternating magnetic field reduces carbonate precipitation, extending durability in alkaline and neutral electrolytes.
Design of CO2 electroreduction (CO2R) interfaces requires understanding of the dynamic interplay among reactants, surface species and ions. Simplified ideal frameworks, which are conventionally employed to identify these dependencies, provide limited insights under relevant conditions. Here we resolve species interplay in membrane electrode assemblies up to high current densities (1 A cm−2), combining operando Raman spectroscopy and ab initio molecular dynamics. We identify a key role of water ordering in regulation of access to the interface along different operation regimes. Initially, double-layer water exhibits a dominant four-hydrogen-bond (4-HB) coordination with a random configuration. With increasing current density, water rearranges to a three-hydrogen-bond coordination and sits H-down close to the surface, acting as the primary proton source for CO2R and generating adsorbed hydroxides. Eventually, this results in carbonate build-up that increases the concentration of H-down 4-HB water, restricting interface access to COx reactants and promoting hydrogen evolution. These results increase our understanding of CO2R interfaces up to application-relevant current densities. Understanding the dynamic interplay between all components in complex electrocatalytic systems is crucial to advancing their performance. Here operando Raman spectroscopy is used in combination with molecular dynamics simulations to establish the role of water ordering in the mechanism of electrocatalytic CO2 reduction over a range of current densities and under practical conditions.
Efforts to improve carbon dioxide electroreduction have often focused on the catalyst. Now, by focusing on the gas instead, non-thermal plasma activation can unlock products that are not accessible through conventional electrocatalysis.
Biosynthesis of penicillin and cephalosporin antibiotics involves the oxidation of the tripeptide δ-(l-α-aminoadipoyl)-l-cysteinyl-d-valine (ACV) to give the conformationally strained bicyclic penicillin ring system, as catalysed by the Fe(II)-dependent oxidase isopenicillin N synthase (IPNS). The structures of the precursors for the sequential β-lactam and thiazolidine ring forming steps in IPNS have remained elusive. Here we studied the reaction of anaerobic IPNS:Fe(II):ACV microcrystals with O2 using time-resolved serial femtosecond crystallography and X-ray emission spectroscopy. High-resolution structures reveal that ACV cysteinyl oxidation produces a thioaldehyde that unexpectedly does not coordinate the iron centre. The use of deuterium-labelled ACV enabled the observation of a monocyclic β-lactam with restoration of the Fe–S bond. Together with mutagenesis, spectroscopic and computational studies, the results support Fe(IV)-mediated penicillin formation involving active-site water molecules. These findings provide structural insight into IPNS catalysis, inform on the wider Fe(II) oxygenase superfamily and highlight the power of X-ray free-electron laser methods for resolving transient enzymatic intermediates. The structural basis of key intermediates in isopenicillin N synthase catalysis, underlying β-lactam biosynthesis, has remained incomplete. Now time-resolved X-ray free-electron laser studies capture transient states and reveal how protein dynamics and solvent networks govern oxygen activation and ring formation.
Sulfides catalyse aromatic halogenations but often struggle with less reactive arenes. Now, breaking the symmetry of existing sulfide catalysts allows sulfur orbital interactions that can expand the scope of these reactions.
