EES catalysis最新文献

An accurate model for predicting TiO₂ photocatalytic hydrogen evolution reaction (HER) rates is hereby presented. The model was constructed from a database of 971 entries extracted predominantly from the open literature. A key step that enabled high accuracy lies in the use of active photon flux (AcP, photons with energy equal to and greater than the bandgap energy of the photocatalyst) as the input feature describing the irradiation. The quantification of AcP, besides being a more direct feature describing the photocatalyst excitation, circumvents the use of lamp power ratings and light intensities as ambiguous inputs as they encompass varying degrees of AcP depending on the irradiation spectra. The AcP unifies four other key performing features (out of 46 initially screened), i.e., cocatalyst work functions, loadings of cocatalyst, alcohol type and concentrations, to afford a physically-intuitive model that can be generalized to a wide range of experimental conditions. The inclusion of AcP as an input to the machine learning model for HER prediction leads to a mean absolute error of 7 μmol h, which is a 90% reduction when compared to a model that does not use AcP. Verification of untested conditions with high HER rates, identified through Bayesian optimization, saw less than 9% deviation from the physically-measured kinetics, thus confirming the validity of the model.

Hydrogen peroxide (H₂O₂) is a valuable green oxidant with a wide range of applications. Furthermore, it is recognized as a possible future energy carrier achieving safe operation, storage and transportation. The photochemical production of H₂O₂ serves as a promising alternative to the waste- and energy-intensive anthraquinone process. Following the 12 principles of Green Chemistry, we demonstrate a facile and general approach to sustainable catalyst development utilizing earth-abundant iron and biobased sources only. We developed several iron oxide (FeO_x) nanoparticles (NPs) for successful photochemical oxygen reduction to H₂O₂ under visible light illumination (445 nm). Achieving a selectivity for H₂O₂ of >99%, the catalyst material could be recycled for up to four consecutive rounds. An apparent quantum yield (AQY) of 0.11% was achieved for the photochemical oxygen reduction to H₂O₂ with visible light (445 nm) at ambient temperatures and pressures (9.4–14.8 mmol g⁻¹ L⁻¹). Reaching productivities of H₂O₂ of at least 1.7 ± 0.3 mmol g⁻¹ L⁻¹ h⁻¹, production of H₂O₂ was further possible via sunlight irradiation and in seawater. Finally, a detailed mechanism has been proposed on the basis of experimental investigation of the catalyst's properties and computational results.

Electrocatalytic CO₂ reduction is regarded as one of the most promising strategies for converting CO₂ to valuable chemicals or fuels. However, developing efficient catalysts for enhanced multi-carbon production at industrial current densities is still a great challenge. Herein, we report a novel method to prepare bimetallic Cu–Zn catalysts for electrocatalytic CO₂ reduction using magnetron sputtering and subsequent electrochemical cyclic voltammetry treatment. Due to the increase of the Cu–Zn interface and the shortening of mass transfer distance, the bimetallic Cu–Zn catalysts showed a faradaic efficiency (FE) of 29.3% for ethanol production at a current density of −250 mA cm⁻² when testing in a flow cell. Our work provides a new strategy for the design and synthesis of bimetallic catalysts for electrocatalysis.

In this review, recent advances in the use of platinum single-crystal surfaces in electrochemistry are addressed. The starting point is the voltammetric characterization in a supporting electrolyte because the profile can be used as a fingerprint of the surface, allowing the surface quality and solution cleanliness to be established. The signals appearing in these voltammograms have been assigned to the adsorption of H, OH, and the anions in the supporting electrolyte. Then, the distinctive behavior of the Pt(111) electrode regarding the adsorption of species and the electrocatalysis in comparison with the other single-crystal surfaces is discussed. For the H/OH adsorption, the (111) ordered domain is the only one in which both processes appear in different potential windows. For the remaining ordered domains, steps, and kinks, both processes overlap, giving rise to signals that correspond to the competitive adsorption/desorption of OH and H. This fact implies that OH may be adsorbed on the surface at potentials as low as 0.15 V, which is a paradigm shift in the up-to-now prevailing understanding of the electrochemical behavior of platinum electrodes and has important implications for the elucidation of the mechanism of electrocatalytic reactions. The effects of this new knowledge on the proposed reaction mechanisms for the oxidation of CO and small organic molecules and the reduction of oxygen and hydrogen peroxide are discussed in detail. Since the elucidation of the reaction mechanisms requires in many cases the use of computational modeling, the conditions that the models should fulfill to reach valid conclusions are discussed. Relevant examples, which highlight the importance of the local structure of the interphase in the electrochemical behavior are given.

Supported metal oxide nanoclusters (MeO-NCs) have gained significant attention for their remarkable versatility in various energy and sustainability applications. Despite rapid advancements in atomic-scale synthesis and characterization techniques, the rational design of MeO-NCs with desired catalytic properties remains challenging. This challenge arises from the elusive and difficult-to-quantify structure-catalytic property relationships, particularly in the case of amorphous nanoclusters. Exploiting first-principles calculations at the density functional theory (DFT) level, we conducted a systematic investigation into the growth, geometries, and catalytic performance of a series of tetra-copper oxide nanoclusters (Cu₄O-NCs) for methane activation. Focusing on the most representative geometries, we applied machine learning to extract two physically insightful descriptors involving the spin density, the p-band center of the oxygen site, and the d-band center of adjacent Cu sites. These descriptors enable us to predict free energy barriers associated with both the homolytic and heterolytic mechanisms of methane activation. This descriptor-driven approach enables rapid and intuitive prediction of the preferred reaction mechanism. Our findings lay a solid foundation for future advancements in catalysts based on amorphous nanoclusters and provide valuable insights into the mechanistic landscape of methane activation.

Hydrogen production with high efficiency and low CO selectivity in methanol steam reforming (MSR) is of pivotal importance. However, there is limited understanding of the active sites and reaction mechanisms during catalysis. In this study, we maximized the interfacial site, known as the active component in MSR, of Ni–CeO_x by atomically dispersed Ni and Ce over the carbon–nitrogen support to generate the Ni and Ce dual-atomic catalyst (DAC), which achieved 6.5 μmol_H2 g_cat.⁻¹ s⁻¹ H₂ generation rate and 0.8% CO selectivity at 99.1% methanol conversion at 513 K. The finely dispersed Ni and Ce structure was confirmed by systematic characterization of AC HAADF-STEM and EXAFS. Electron transfer from Ce to Ni was confirmed simultaneously by quasi-in situ XPS analysis. Moreover, the reaction mechanism of methanol steam reforming was clarified by combining kinetic studies with isotope-tracing/exchange analysis (i.e., KIEs and steady-state isotopic transient kinetic analysis (SSITKA)), which suggests that the steam reforming consists of two tandem reaction processes: methanol decomposition (MD) and water–gas shift (WGS) reaction, with methanol and water activation at independent active sites (e.g., Ni and oxygen vacancy over CeO_x), and that hydrogen generation was primarily determined by both C–H bond rupture and O_L–H (O_L represents the lattice oxygen) cleavage within methoxy and hydroxyl groups, respectively, with the catalytic surface mainly covered by CO and methoxy groups. A shift of WGS involvement in hydrogen generation from negligibly influenced to significantly promoted was selectively observed once modifying the reaction from differential conditions to a high methanol conversion regime, and two quantification methods have been established by comparing the molecule ratio between CO and CO₂ or H₂.

Reactive carbon capture (RCC), an integrated CO₂ capture and conversion process that does not require generating a purified CO₂ stream, is an attractive carbon management strategy that can reduce costs and energy requirements associated with traditionally separate capture and conversion processes. Dual function materials (DFMs) comprised of co-supported sorbent sites and catalytic sites have emerged as a promising material design to enable RCC. DFMs have been extensively studied for methane production, but the noncompetitive economics of methane necessitates the development of DFMs to target more valuable, useful, and versatile products, like methanol. Herein, we report the development of modified Cu–Zn–Al mixed oxide (Alk/CZA, Alk = K, Ca) DFMs for combined capture and conversion of CO₂ to methanol. CO₂ chemisorption, in situ DRIFTS characterization, and co-fed hydrogenation performance revealed that K and Ca have different effects on the CO₂ capture and catalytic behavior of the parent CZA. K-modification resulted in the greatest promotional effect on capture capacity but the most detrimental effect on co-fed hydrogenation catalytic activity. Interestingly, when used in a cyclic temperature-and-pressure-swing RCC operation, K/CZA exhibited a greater conversion of adsorbed CO₂ (94.4%) with high methanol selectivity (46%), leading to greater methanol production (59.0 μmol g_DFM⁻¹) than the parent CZA or Ca/CZA (13.2 and 18.9 μmol g_DFM⁻¹, respectively). This study presents the foundational methodology for the design and evaluation of novel DFMs to target renewable methanol synthesis, highlighted by a critical learning that co-fed CO₂ hydrogenation performance is not an effective indicator of RCC performance.

Selective catalytic reduction of NO with NH₃ (NH₃-SCR) is a promising technology to reduce the emission of nitrogen oxides (NO_x) from diesel engines and industrial flue gases. Due to their advantages of variable valence and high stability, Cu-based catalysts exhibit superior activity and have been widely employed in the NH₃-SCR reaction. Herein, we expound the reaction mechanism of NH₃-SCR, and summarize the comprehensive advances of Cu-based catalysts (Cu-based small-pore zeolites and Cu-containing metal oxides) developed in the last decade. In this review, the challenges and prospects for Cu-based catalysts are presented to meet the industrial need, and efficient design strategies for promoting the NH₃-SCR performance of Cu-based catalysts through support derivation, precursor optimization engineering, secondary metal doping, crystal structure regulation, preparation method modification and interaction and interface engineering are comprehensively proposed and discussed. These proposed strategies are confirmed to be beneficial for enhancing catalysis by accelerating acid and redox cycles. Besides, we sum up the poisoning mechanism of impurities from flue gas on active sites, and provide the corresponding anti-inactivation measures to inhibit the deactivation of catalysts. Finally, we hope to focus on the current opportunities and challenges faced by Cu-based catalysts, further promoting their development and achieving practical applications.

Aqueous rechargeable static zinc–iodine (Zn–I₂) batteries are regarded as competitive candidates for next-generation energy storage devices owing to their safety and high energy density. However, their inherent limitations such as the shuttle effect, sluggish electrochemical kinetics, and the poor electrical conductivity of iodine have been challenging to mitigate when using methods that confer polarity to the surface of the carbon host through nitrogen doping. Moreover, the considerable prevalence of inactive pyridinic N sites significantly impedes the establishment of approaches to overcome issues associated with redox kinetics and iodine utilization. Herein, single Ni atoms were incorporated into an electrochemically inactive N-doped carbon matrix by carbonizing a zeolitic imidazolate framework and then thermally activating the Ni ions adsorbed onto the carbonized product. The single Ni atoms modulated the electronic structure of the surrounding N-doped carbon matrix, thereby improving its ability to adsorb polyiodides and exhibit bifunctional catalytic activity for iodine reduction and oxidation reactions. Consequently, the assembled Zn–I₂ battery delivered an outstanding rate performance (193 mA h g⁻¹ at a current density of 6 A g⁻¹) and ultralong cyclability (10 000 cycles at a current density of 4 A g⁻¹). Overall, this study illuminates the merits of using single-atom catalysts to revitalize inactive N pyridinic sites, thereby providing a promising direction for further advancement of Zn–I₂ batteries.

Anion exchange membrane water electrolyzers (AEMWEs) are poised to play a key role in reducing capital cost and materials criticality concerns associated with traditional low-temperature electrolysis technologies. To accelerate the development and deployment of this technology, an in-depth understanding of cell materials integration is essential. Notably, the complex chemistries and interactions within the catalyst layer (consisting of the anode/cathode catalyst, anion exchange ionomer, and their interfaces with the transport layers and membrane) collectively influence overall cell performances, lifetimes, and costs. This review outlines recent advances in understanding the catalyst layer in AEMWEs. Specifically, electrode development strategies (including catalyst deposition techniques and configurations as well as transport layer design strategies) and our current understanding of catalyst–ionomer interactions are discussed. Effects of cell assembly and operational variables (including compression, temperature, pressure, and electrolyte conditions) on cell performance are also discussed. Lastly, we consider cutting-edge in situ and ex situ diagnostic techniques to study the complex chemistries within the catalyst layer as well as discuss degradation mechanisms that arise due to the integration of cell components. Simultaneously, comparisons are made to proton exchange membrane water electrolyzers (PEMWEs) and liquid alkaline water electrolyzers (LAWE) throughout the review to provide context to researchers transitioning into the AEMWE space. We also include recommendations for standard operating procedures, configurations, and metrics for comparing activity and stability.