Articles in 2023

Proton exchange membrane fuel cell catalyst layers (CLs) have complex structures that largely determine their performance and durability. Their three-dimensional morphology and component spatial distribution is still poorly understood. This comprehensive work reports one of the first cryogenic transmission electron tomography reconstructions of a full commercial CL section, including challenging-to-image ionomer distribution.

The issue of gas solubility has profound implications for studying the activity of oxygen reduction reaction electrocatalysts. Aqueous solutions endowed with permanent microporosity — termed microporous water — could be the answer.

Design of artificial photosynthetic systems that mimic the complex supramolecular structures in natural systems remains a grand challenge. Here self-assembled nanomicelles containing Zn porphyrins and Co porphyrins as photosensitizer and catalyst achieve selective photocatalytic CO₂-to-CH₄ conversion in water.

Saccharomyces cerevisiae can be engineered to slowly use methanol; however, a co-carbon source is usually required to support its growth. Now, a Saccharomyces cerevisiae strain that can use methanol as the sole carbon source for growth, and produce value-added bioproducts, is developed.

Electrocatalytic processes involving gas molecules are generally limited by low solubility in aqueous solutions. Here water endowed with permanent microporosity by silicalite-1 nanocrystals is used to concentrate O₂, allowing the measurement of the intrinsic activity of a Pt/C catalyst in the oxygen reduction reaction.

Nitrogenases are of high interest due to their ability to form NH₄⁺ by reduction of atmospheric dinitrogen. However, the detailed architecture of the Fe-only isoform remained unknown. Now, a high-resolution crystal structure of Fe-nitrogenase is solved, deepening the understanding of nitrogenase catalysis.

The discovery of the Tetrahymena group I intron’s self-splicing defined RNAs as capable catalysts. Now, cryogenic electron microscopy structures of this ribozyme have revealed large conformational changes and mechanistic details of its two-step mode of action.

In a standard electrochemistry experiment, the electrochemical signal reports on all electron transfer, chemical, and diffusion steps between the anode and cathode. Now, a membrane reactor decouples each of these steps to enable direct measurement of elementary reaction steps in ways that are otherwise not possible.

Electrochemical hydride (H^–) transfer has been an elusive process. Now, using well-designed model systems, the phenomenon has been isolated and further demonstrated as a practical synthetic method with H₂ gas as the hydrogen source.

Charge transfer and chemical kinetics both contribute to the overall overpotential that is observed in a typical electrocatalytic experiment, but it remains difficult to resolve the individual contributions. Here a Pd membrane double cell is used to separate the charge transfer and chemical steps in the hydrogen evolution reaction to evaluate how experimental conditions affect the individual steps.

Electrocatalytic nitrate reduction represents an opportunity to generate ammonia under ambient conditions, yet the efficiency has been limited by the large overpotential required. Here, a Ru–Co alloy demonstrates a three-step relay mechanism involving a spontaneous redox step that reduces the overpotential for the process.

The Lebedev process is an established approach to convert ethanol into butadiene catalysed by silica–magnesia prepared by the so-called wet-kneading method. However, the role and impact of this wet-kneading approach have not been fully uncovered. Here the authors reveal important aspects of this process and elucidate the role of the different active sites it generates within silica–magnesia.

Although homogeneous hydride transfer reactivity is well understood, the heterogeneous counterpart at metal surfaces remains rather unexplored. This work introduces the electrocatalytic hydrogen reduction reaction, which in net reduces H₂ to reactive hydrides via the intermediacy of surface M−H species. The study reveals that hydride transfer from surface M−H species can be driven by electrical polarization.

The full potential of the well-known platinum oxygen reduction catalyst has not been realized in membrane electrode assembly for fuel cells due to the detrimental impacts of the required ionomer layer. Here the authors show how cyclohexanol can block the interaction between Pt and sulfonate groups of Nafion with benefits for reaction kinetics and mass transport.

The catalyst layer in proton-exchange membrane fuel cells involves the complex and crucial interplay between an ionomer network and metallic nanoparticles supported on carbons, but current methods are unable to describe it with high resolution. Now electron tomography at cryogenic temperatures and deep learning algorithms are used to provide quantitative three-dimensional imaging at nanometre resolution of a fuel cell catalyst layer structure.

Conjugate cyanation of linear α,β-unsaturated aldehydes has remained an unsolved synthetic challenge. Now a method based on organocatalysis and photoredox catalysis is developed that facilitates this process asymmetrically, leading to an exclusive 1,4-chemoselectivity.