Faraday Discussions最新文献

The Bethe surface represents the X-ray scattering cross section as a function of momentum transfer and energy loss, mapping the electronic spectrum of the target via the inelastic transition matrix elements. By effectively merging spectroscopy and scattering, a time-resolved measurement of the molecular Bethe surface during a chemical reaction could reveal details of the reaction path through the manifolds of electronic states and conical intersections. However, conventional imaging detectors used for X-ray scattering lack energy resolution. We demonstrate here how the Bethe surface can be measured with the help of a spectral filter in the form of a thin zinc metal foil inserted between the target and the detector. Harnessing the inherent stochasticity of X-ray pulses generated by self-amplified spontaneous emission at X-ray free-electron lasers (XFELs), we demonstrate how the double-differential X-ray scattering cross section can be reconstructed using a novel ghost-imaging algorithm. Corrections for fluorescence from the metal filter need to be applied. The method requires excellent signal levels that can be obtained for molecules with large scattering cross sections, but advances in XFEL technology promise opportunities for a wide range of applications.

Electrocarboxylation of organic substrates offers a promising route for CO₂ utilization in sustainable synthesis, but its practical application is limited by poor selectivity arising from competing electrochemical pathways. Here, we investigate the electrocarboxylation of benzyl bromide, benzaldehyde, and styrene on polycrystalline copper electrodes in acetonitrile to elucidate how substrate structure and applied potential govern reaction selectivity. By combining cyclic voltammetry, bulk electrolysis, and in situ FTIR spectroscopy, we found electrocarboxylation does not follow a single mechanistic pathway but is instead controlled by the competition between substrate activation, CO₂ reduction, and parallel side reactions. Benzyl bromide exhibits the highest electrocarboxylation efficiency, consistent with facile substrate activation and rapid coupling with CO₂. In contrast, benzaldehyde forms a ketyl intermediate that predominantly undergoes dimerization and hydrogenation, limiting carboxylation. For styrene, the more negative potentials required for substrate activation overlap with CO₂ reduction, resulting in a regime dominated by CO₂-derived products and minimal electrocarboxylation. These findings demonstrate that the relative alignment of substrate and CO₂ reduction potentials defines distinct reactivity regimes that determine electrocarboxylation selectivity. This mechanistic framework contributes to the basis for rational design of electrochemical systems for efficient CO₂ utilization.

Management of excess organic nitrogen in wastewater-derived sludge is increasingly important due to the high cost of sludge disposal. Recovering ammonia from organic nitrogen in sludge through electrolysis offers a promising approach to managing this nitrogen waste stream while generating economic value. Despite the abundance of high-molecular-weight nitrogen compounds in sludge, limited progress has been made in understanding how organic nitrogen can be directly and efficiently transformed into ammonia without microorganisms. Here, we investigate the abiotic reaction pathways for converting glycine into ammonia on nickel-based electrodes. Glycine was chosen as a model sludge-based organic molecule due to glycine's prevalence in activated sludge. We demonstrate, through cyclic voltammetry and X-ray photoelectron spectroscopy, that trace iron present in the electrolyte forms FeNi(OH)₂ at the surface of the Ni electrode. As the Fe concentration increases, the product selectivity shifts. Formate selectivity increases from 2.5% to 18% when Fe is present, while glycolate is only measured when Fe is absent (ca. 30% selectivity). Ammonia selectivity increases from 70% to 82% when Fe is present in the electrolyte. Possible pathways for formate, acetate, glycolate, glyoxylate, ammonia, nitrite, and nitrate are discussed. This work aims to inform future catalyst design strategies to steer organic nitrogen conversion to ammonia.

The shift from traditional fossil-fuel-based chemical production to a renewable e-chemical industry requires innovation in the design of catalytic and electrocatalytic systems for both initial production of platform hydrocarbons and their subsequent upgrading to a core suite of feedstocks and chemical intermediates. To this end, we require selective and efficient catalytic systems that operate under relatively mild conditions. We have recently developed a new approach, termed Co-Operative Redox Enhancement (CORE), to the design of catalytic systems that leverage electrocatalytic driving forces to substantially enhance the activity of what, at first glance, would be considered a thermal catalytic process. Dissimilar, physically separated but electrochemically connected catalytic nanoparticles will establish a spontaneous, nanoscale, electrochemical gradient between them due to differences in the electrocatalytic selectivity of each particle towards the desired half reactions. This leads to polarization of the nanoparticles and associated enhancement in their selectivity and activity towards the half reactions, driving an overall increase in catalytic turnover. The extent of polarization is quantifiable and the impact on overall catalytic turnover is predictable through an electrochemical approach based on modified corrosion theory. This new approach to the design of catalytic systems has wide-ranging implications for the design of thermal and electrocatalytic systems for the e-chemical industry and beyond. In this work, we discuss the oxidative dehydrogenation of benzyl alcohol utilizing coupled Au/C and Pd/C catalysts as an exemplar of CORE. The role of CORE is demonstrated through a combination of thermocatalytic and electrocatalytic experiments, pointing towards CORE as an approach to design and implement both thermal and electrochemical catalytic systems for efficient e-chemical production.

The integration of CO₂ capture and conversion into a single system has been suggested as an efficient and transformative approach for enabling the conversion of CO₂ to high-value chemicals and fuels to reduce the reliance of hard-to-decarbonize industries on fossil fuels. One of the challenges of the electrochemical reduction of CO₂ is the low solubility of CO₂ in aqueous electrolyte. In this study, we synthesized a variety of multiscale-particle organic hybrid materials (MOHMs) composed of varying SiO₂ core sizes across 5 orders of magnitude, containing two distinct polymer canopies (HPE and PEI) with varying CO₂ binding strengths, and investigated their effect on CO₂RR over a nanoparticle Ag catalyst. MOHM-I-HPE-containing electrolytes were observed to exhibit a reverse volcano relationship between CO faradaic efficiency (FE) and core size, with 7 nm MOHM-I-HPE achieving similar CO FE to 0.1 molal KHCO₃ though at reduced current densities, while 10 µm MOHM-I-HPE exceeded the performance of the conventional electrolyte (76% vs. 65% FE for CO), while simultaneously exhibiting increased CO current density and decreased H₂ current density relative to the conventional electrolyte. Structural investigations of the electrodes after CO₂RR indicate that the small-core sizes form a persistent adlayer that facilitates CO₂ transport to the surface, while large-core sizes transiently deliver CO₂ to the electrode. In contrast, MOHM-I-PEI additives drastically reduced CO₂RR as the strong chemisorption prevents effective conversion of the bound CO₂. These findings provide valuable insight into the effective design of particle-based electrolyte additives and how CO₂ can be captured and delivered to the surface of catalysts, while tuning the local reaction environment.

The Projected Forces and Momenta (PFM) decoherence correction has recently been introduced [J. Chem. Theory Comput., 2025, 21, 10645] and successfully applied for trajectory surface-hopping (TSH) simulations describing the coupled electron-nuclear dynamics originating from coherent superpositions of molecular electronic states generated by broadband laser excitation. In this work, we extend the capabilities of TSH-PFM for the simulation of a broader range of nonadiabatic dynamics. First, we showcase the inclusion of the explicit interaction with a broadband pulse and apply it to the LiH molecule, obtaining very good agreement with full quantum-mechanical reference calculations. We then demonstrate how a recently proposed post-processing approach to incorporate a posteriori initial electronic coherences onto pulse-independent TSH trajectories [J. Chem. Theory Comput., 2026, 22, 1224] allows for the evaluation of the dynamics arising from initial electronic coherences across a large manifold of few-fs UV pulses, without recalculating the nuclear dynamics for every set of parameters. This is exemplified for the glycine molecule, systematically varying the central frequency and bandwidth of the broadband excitation pulse. Finally, we scrutinize TSH-PFM for the ring-opening reaction in 1,2-dithiane. On the one hand, we show that TSH-PFM predicts the same nonadiabatic dynamics as established TSH approaches throughout the whole propagation of 700 fs. On the other hand, we find that an initial superposition of the two lowest excited states, albeit decohering before the ring opens, accelerates the structural dynamics by several tens of fs compared to that starting exclusively from the lowest excited state due to the population of the second excited state.

With a backdrop of energy transition and geopolitical tensions, efficient biomass-assisted hydrogen production with non-platinum group metals is sought. Understanding of the related reaction mechanisms is crucial for the rational development of effective electrocatalytic materials but said mechanisms can sometimes be uncritically trusted and cited extensively in contexts deviating from the original working hypotheses. This is the case for Fleischmann's mechanism for the glucose oxidation reaction (GOR) on nickel, where the initial information was progressively modified and extrapolated carelessly. In line with recent research, this work attempts to tackle some preconceptions about the glucose oxidation reaction on nickel and nickel-based electrodes. The electrooxidation of xylose, another major product of lignocellulosic biomass, but very scarcely discussed in the literature, is also studied, alone and in a biomass-like mixture with glucose. Based on electrochemical (cyclic voltammetry, chronoamperometry and impedance spectroscopy) and analytical (product distribution obtained during 5 hours aldose electrolysis experiments) results on different anode materials (Ni foam, Ni@Ni(O_xH_y)/C and Ni₅Mn₅O_x/C), the aldose electrooxidation mechanisms are revisited. Additionally, this study addresses some previously unexplored questions concerning this system such as material poisoning, the viability of using a membrane in GOR electrolysis cells, or the impact of aldose chemical degradation by the alkaline electrolyte on selectivity interpretation.

Although potential-induced surface restructuring of catalysts is well documented, light irradiation can further enhance this phenomenon, leading to significant changes in catalytic activity and product selectivity. Despite its significance, light-assisted surface reconstruction has not been adequately investigated in previous studies. In this work, we compare the yield and selectivity of ammonia production at a CuO/C photocathode under applied potential and combined light-potential conditions, demonstrating how dynamic surface modulation influences catalytic performance. During the photoelectrochemical nitrate reduction reaction (PEC-NTRR), the CuO/C photocathode achieves a maximum ammonia yield of ∼36.9 µmol h^-1 cm^-2 at -1.4 V (vs. Ag/AgCl) under illumination, representing a 2.8-fold enhancement over dark conditions at the same potential. Meanwhile, the maximum nitrite yield reaches ∼43 µmol h^-1 cm^-2 at -1.1 V, nearly 90 times higher than in the dark. This significant increase in both ammonia and nitrite formation under illumination clearly indicates that light plays a crucial role in altering product yield and selectivity. In situ X-ray absorption spectroscopy revealed light-dependent evolution of the CuO local structure under applied potential. While no significant structural transformation occurs at open-circuit potential, applying a negative potential (-1.3 V vs. Ag/AgCl) induces partial reduction of Cu²⁺ to Cu(0) (Cu^δ+), which becomes more pronounced when combined with light irradiation, leading to a more dynamically modulated Cu(0) state (Cu^(δ*)+) that affects product selectivity. In situ FTIR spectroscopy tracks the formation of surface-bound intermediates, showing that the reaction proceeds through successive deoxygenation and hydrogenation steps consistent with the conventional mechanism. Overall, this study establishes a clear correlation between light-driven local structural modulation and the resulting enhancement in product yield and selectivity.