Nature Catalysis最新文献

Electrochemical interfaces between polymer electrolytes and electrodes are central to electrochemical devices in the global transition towards renewable energy. Here we show that the adsorption and desorption of sulfonates in Nafion on Pt(111) involve distinct elementary steps, with the latter proceeding through a coupled cation–electron transfer. Adsorbed sulfonates not only block a fraction of surface Pt sites but, more importantly, generate two additional types of surface adsorbate, OH_Nafion and O_Nafion, which exhibit distinct kinetic properties from adsorbed OH and O on bare Pt(111), respectively. The impact of the adsorption of sulfonate groups in Nafion on the activity of the oxygen reduction reaction (ORR) on Pt cannot be rationalized by existing thermodynamic descriptors. The reduced ORR activity on the Nafion-covered Pt(111) is caused by the kinetically hindered *O→*OH conversion and *OH reduction on sites close to adsorbed sulfonates.

The electrochemical reduction of CO₂ is sensitive to the microenvironment surrounding catalytic active sites. Although the impact of changing electrolyte composition on rates has been studied intensively in aqueous electrolytes, less is known about the influence of the electrochemical environment in non-aqueous solvents. Here we demonstrate that organic alkylammonium cations influence catalytic performance in non-aqueous media and describe a physical model that rationalizes these observations. Using results from kinetic, spectroscopic and computational techniques, we argue that the strength of the electric field at the catalyst surface is sensitive to the molecular identity of the organic cation in the electrolyte. This is true irrespective of solvent, electrolyte ionic strength or electrolyte anion. Our results suggest that changes in the interfacial electric field strength can be attributed to differences in the cation–electrode distance. Changes in the electric field strength affect CO formation rates as they modify the energetics of the kinetically relevant CO₂ activation step.

Biorefinery technologies that convert lignin into platform chemicals are essential to reduce our future dependence on fossil resources. In these technologies, a key process is the acid-catalysed O demethylation of guaiacol derivatives in hot-pressurized water using Brønsted mineral acids or microporous zeolites. The fundamental understanding of how hydronium ions behave in a confined environment versus bulk is still limited. Here we investigate the O demethylation of guaiacol in hot-pressurized water with HCl or H-BEA zeolite catalysts to elucidate the impact of zeolite microporosity on reaction mechanisms and rates. Operando molecular simulations combined with experimental kinetic studies reveal that, regardless of the catalyst type, O demethylation follows a concerted O-activated S_N2 mechanism. The reaction rate is higher in the zeolite due to more active, under-coordinated hydronium ions. Additionally, the molecular organization of solvent and reactants around the confined active site plays a crucial role in modulating the association of the reacting species and the reaction kinetics.

Methods for direct enantioselective oxidation of C(sp³)–H bonds will revolutionize the preparation of chiral alcohols and their derivatives. Enzymatic catalysis, which uses key metal-oxo species to facilitate efficient hydrogen atom abstraction, has evolved as a highly selective approach for C–H oxidation in biological systems. Despite its effectiveness, reproducing this function and achieving high stereoselectivity in biomimetic catalysts has proven to be a daunting task. Here we present a copper-based biomimetic catalytic system that achieves highly efficient asymmetric sp³ C–H oxidation with C–H substrates as the limiting reagent. A Cu(II)-bound tert-butoxy radical is responsible for the site-selective C–H bond cleavage, which resembles the active site of copper-based enzymes for C–H oxidation. The developed method has been successfully accomplished with good functional group compatibility and exceptionally high site- and enantioselectivity, which is applicable for the late-stage oxidation of bioactive compounds.

Correction to: Nature Catalysis https://doi.org/10.1038/s41929-024-01262-w, published online 13 December 2024.