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In catalysis, determining the relationship between the dynamic electronic and atomic structure of the catalysts and the catalytic performance under actual reaction conditions is essential to gain a deeper understanding of the reaction mechanism since the structure evolution induced by the absorption of reactants and intermediates affects the reaction activity. Hard x-ray spectroscopy methods are considered powerful and indispensable tools for the accurate identification of local structural changes, for which the development of suitable in situ reaction cells is required. However, the rational design and development of spectroscopic cells is challenging because a balance between real rigorous reaction conditions and a good signal-to-noise ratio must be reached. Here, we summarize the in situ cells currently used in the monitoring of thermocatalysis, photocatalysis, and electrocatalysis processes, focusing especially on the cells utilized in the BL14W1-x-ray absorption fine structure beamline at the Shanghai Synchrotron Radiation Facility, and highlight recent endeavors on the acquisition of improved spectra under real reaction conditions. This review provides a full overview of the design of in situ cells, aiming to guide the further development of portable and promising cells. Finally, perspectives and crucial factors regarding in situ cells under industrial operating conditions are proposed.

The quantitative understanding of how atomic-level catalyst structural changes affect the reactivity of the electrochemical CO2 reduction reaction is challenging. Due to the complexity of catalytic systems, conventional in situ X-ray spectroscopy plays a limited role in tracing the underlying dynamic structural changes in catalysts active sites. Herein, operando high-energy resolution fluorescence-detected X-ray absorption spectroscopy was used to precisely identify the dynamic structural transformation of well-defined active sites of a representative model copper(II) phthalocyanine catalyst which is of guiding significance in studying single-atom catalysis system. Comprehensive X-ray spectroscopy analyses, including surface sensitive Δμ spectra which isolates the surface changes by subtracting the disturb of bulk base and X-ray absorption near-edge structure spectroscopy simulation, were used to discover that Cu species aggregated with increasing applied potential, which is responsible for the observed evolution of C2H4. The approach developed in this work, characterizing the active-site geometry and dynamic structural change, is a novel and powerful technique to elucidate complex catalytic mechanisms and is expected to contribute to the rational design of highly effective catalysts.

A well-defined Fe-based single-atom catalyst for electrocatalytic CO2 reduction to CO was synthesized via a facile pyrolysis of Fe-doped ZIF-8. Fe single-atomic sites exhibit optimum activity in producing CO with nearly 100% faradaic efficiency.

A super anti-sintering Pt nanoparticle catalyst on LaNiO3 support is synthesized by introducing Ru ions into LaNiO3 to produce the strong interface bonding between the Pt nanoparticle catalyst and LaNiO3 support.

Developing the large-scale preparation of non-noble metal catalysts with high performance is crucial for promoting the electrochemical production of hydrogen from water. In this work, a novel TiO2@FeNi2S4 (TiO2@FNS) branch nanoflake array on Ni foam can be prepared at a large scale (50 cm2) by combining an atomic-layer-deposited (ALD) TiO2 skeleton with one-step facile low-temperature (

Proton-exchange membrane fuel cells (PEMFCs) are limited by their extreme sensitivity to trace-level CO impurities, thus setting a strict requirement for H2 purity and excluding the possibility to directly use cheap crude hydrogen as fuel. Herein, we report a proof-of-concept study, in which a novel catalyst comprising both Ir particles and Ir single-atom sites (IrNP @IrSA -N-C) addresses the CO poisoning issue. The Ir single-atom sites are found not only to be good CO oxidizing sites, but also excel in scavenging the CO molecules adsorbed on Ir particles in close proximity, thereby enabling the Ir particles to reserve partial active sites towards H2 oxidation. The interplay between Ir nanoparticles and Ir single-atom centers confers the catalyst with both excellent H2 oxidation activity (1.19 W cm-2 ) and excellent CO electro-oxidation activity (85 mW cm-2 ) in PEMFCs; the catalyst also tolerates CO in H2 /CO mixture gas at a level that is two times better than that of the current best PtRu/C catalyst.

Proton exchange membrane fuel cells (PEMFCs) suffer extreme CO poisoning even at PPM level (

The electrochemical CO

WC|WS2 composites with a sponge-like structure were constructed from nanolayers with the aid of NaCl as a template. Each nanolayer was composed of WC|WS2 interfaces by inducing carbon as the interstitial atoms. The local configuration around W atoms was probed by EXAFS. The catalytic activity of WC|WS2 composites for the hydrogen evolution reaction was thoroughly investigated by varying the ratio of WC|WS2. The sponge-like structures not only facilitate the transportation of the electrolyte, but also offer more edge active sites. The introduction of carbon provides W–C bonds, which accelerate the electron transportation and improve the stability of the catalyst in the hydrogen evolution reaction. The hybrid catalyst presents a low overpotential of 103 mV at 10 mA cm−2 and a Tafel slope of 58 mV Dec−1 and possesses great potential for low-cost and larger-scale production applied in catalysis.

A Ru single-atom (Ru SA) catalyst supported on activated carbon was adopted to synthesize 3-pentanone with 83.3% selectivity via heterogeneous ethylene hydroformylation, while 52.1% ethane selectivity was obtained for Ru nanoparticles (Ru NPs). The atomically dispersed Ru species with oxidation state (Ruδ+) and Ru-C4O coordination structure were identified as the active sites for efficient C–C coupling to generate 3-pentanone, while metallic Ru nanoparticles exhibited high activity for ethylene hydrogenation to ethane. Density functional theory (DFT) calculation revealed that the energy barrier of the direct coupling of C2H5CO* with C2H5* to form 3-pentanone on Ru SA was much lower than that on Ru NPs. As a result, the formation of 3-pentanone over Ru SA was more favourable than propanal, which was admittedly generated via coupling of C2H5CO* and H*. This strategy may provide a potential green route for the one-pot synthesis of 3-pentanone with high atomic economy.

Hydrogen economy by water splitting is the indispensable cornerstone for sustainable energy yet it is impeded by sluggish anodic water oxidation. Hence, the rational design of highly efficient electrocatalysts for oxygen evolution is the key to unlocking its wider use. Herein, cobalt–iron selenide nanoframes are reported for the efficient water oxidation, which need only 270 mV overpotential to give a 10 mA cm−2 current density and outperforms most cobalt-based catalysts, and even the benchmarked commercial ruthenium oxides (RuO2). More profoundly, iron doping regulates the local spin state of cobalt species, which further accelerates charge transfer and formation of oxygenated intermediates, and consequently contributes to the enhanced oxygen evolution. This work demonstrates a highly efficient oxygen evolution electrocatalyst and may pioneer a promising approach which involves tuning the local electronic structure to achieve the improved electrocatalysis activities in energy conversion technologies.

The effective activation and utilization of O2 have always been the focus of scientists because of its wide applications in catalysis, organic synthesis, life and medical science. Here, a novel method for activating O2 spontaneously via interfacial oxygen vacancies on carbon-coated TiO2-x to generate reactive oxygen species (ROS) with versatile applications is reported. The interfacial oxygen vacancies can be stabilized by the carbon layer and hold its intrinsic properties for spontaneous oxygen activation without light irradiation, while common surface oxygen vacancies on TiO2-x are always consumed by the capture of H2O to form the surface hydroxyls. Thus, O2 absorbed at the interface of carbon and TiO2-x can be directly activated into singlet oxygen (1O2) or superoxide radicals (·O2-), confirmed both experimentally and theoretically. These reactive oxygen species exhibit excellent performance in oxidation reactions and inhibition of MCF-7 cancer cells, providing new insight into the effective utilization of O2 via oxygen vacancies on metal oxides.

Heterogeneous single-metal-site catalysts have been drawing increasing interests in the field of academy and industry because of the comparable catalytic activity with homogeneous catalyst and easy...

Development of efficient and affordable catalytic systems for direct H2O2 production from abundant resources is necessary to replace the current anthraquinone process and also to enable broader use...

Understanding of the oxygen reduction reaction (ORR) mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells. Herein, a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic (Fe and Co) carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways. The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe. The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen. Interestingly, the pre-adsorption of *OH resulted in the apparent change of metal atoms’ electronic states with the d-band center shifting toward the Fermi level, thereby boosting reaction activity. The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.

Catalytic conversion of the syngas into higher alcohols (HAs) via Fischer–Tropsch (F–T) synthesis is essential due to the widespread applications of HAs. The interfaces of cobalt and cobalt carbide (Co2C) are found to efficiently promote the HAs formation. However, the study on the links between structural evolution of Co–Co2C interfaces and HAs production is still lacking. In this work, Co3O4 with different contents of sodium (Na) as promoters was synthesized and high-pressure F–T reaction (3 MPa) was carried out in the aim of accelerating the Co2C formation and tuning the interfaces of Co–Co2C. XRD, (HR)TEM, ICP, XPS and XAFS were conducted to study the relationship between the variations of Co–Co2C interfaces and HAs production. With the increasing Na contents, the ratios of Co to Co2C decreased as revealed by XAFS and the selectivity of HAs was decreasing. The fitting results from EXAFS revealed that the ratio of Co to Co2C is in direct proportion to the selectivity of HAs. This work provides a theoretical guidance to tune the interfaces of Co–Co2C and improve the HAs production in F–T reaction.

Developing efficient catalysts for steering the electrochemical CO2 reduction reaction (CO2RR) toward high-value chemicals beyond CO and formic acid is highly desirable. Herein, we have developed c...

Summary Identification of the structure-performance relationship at the atomic level is vital for getting a deep understanding of the size-dependence behavior of metal catalysts. Here, an unconventional size dependence of Pt toward selective hydrogenation of p-chloronitrobenzene has been extensively investigated over CeO2 support. An upturned volcanic curve toward the selectivity of p-chloroaniline was found by decreasing the size of Pt from nanoparticles to single atoms. Differences on predominant orbitals among diverse coordination-environment Pt sites were identified to be the key factors influencing the modes of interaction with the C-Cl bond of p-chloroaniline. Specifically, electrostatic repulsion between non-bonding orbitals of Cl and predominant orbitals of Pt sites with high steric hindrance were speculated to be responsible for the suppression of dehalogenation and the high selectivity. This strategy to build correlation between the valence orbitals of active sites and their catalytic behavior could well be expanded to other structure-sensitive reactions and atomically dispersed catalysts.

Development of biomimetic catalytic systems that can imitate or even surpass natural enzymes remains an ongoing challenge 1–3. This is particularly true in the context of accessing non-natural reactions by bioinspired approaches, which offer intriguing possibilities for benign and affordable chemical synthesis 4. Exploiting the untapped potential of inorganic solids by translating complex knowledge in (bio)molecular-based systems may constitute a potentially useful strategy for such purpose 5, but efforts to capitalize on the minimum catalytic unit of a versatile solid matrix have been largely unsuccessful. Here, we show how an all-inorganic biomimetic system bearing robust nitrogen-neighboured single cobalt site/pyridinic-N site (Co-N4/Py-N) pairs can act cooperatively as an oxidase mimic, which renders an engaged coupling of oxygen (O2) reduction with synthetically beneficial chemical transformations. By developing this broadly applicable platform, the scalable synthesis of greater than 100 industrially and pharmaceutically appealing O-silylated compounds via the unprecedented aerobic oxidation of hydrosilane under ambient conditions is demonstrated. Moreover, this heterogeneous oxidase mimic also offers potential for expanding the catalytic scope of enzymatic synthesis. We anticipate that the strategy demonstrated here will pave a new avenue for understanding the underlying nature of redox enzymes and open up a new class of material systems for artificial biomimetics.

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Understanding the dynamic process of interfacial charge transfer prior to chemisorption is crucial to the development of electrocatalysis. Recently, interfacial water has been highlighted in transferring protons through the electrode/electrolyte interface; however, the identification of the related structural configurations and their influences on the catalytic mechanism is largely complicated by the amorphous and mutable structure of the electrical double layer (EDL). To this end, sub-nanometric Pt electrocatalysts, potentially offering intriguing activity and featuring fully exposed atoms, are studied to uncover the elusive electrode/electrolyte interface via operando X-ray absorption spectroscopy during the hydrogen evolution reaction (HER). Our results show that the metallic Pt clusters derived from the reduction of sub-nanometric Pt clusters (SNM-Pt) exhibit excellent HER activity, with an only 18 mV overpotential at 10 mA/cm2 and one-magnitude-higher mass activity than commercial Pt/C. More importantly, a unique Pt-interfacial water configuration with a Pt (from Pt clusters)-O (from water) radial distance of approximately 2.5 A is experimentally identified as the structural foundation for the interfacial proton transfer. Toward high overpotentials, the interfacial water that structurally evolves from "O-close" to "O-far" accelerates the proton transfer and is responsible for the improved reaction rate by increasing the hydrogen coverage.

Precise control of selectivity in hydrogenation reactions is a long-standing challenge. Surface decoration of nanocatalysts with transition-metal oxide nanoparticles (NPs) is an effective strategy ...

The development of high-efficiency electrocatalysts for large-scale water splitting is critical but also challenging. In this study, a hierarchical CoMoSx chalcogel was synthesized on a nickel foam (NF) through an in situ metathesis reaction and demonstrated excellent activity and stability in the electrocatalytic hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The high catalytic activity could be ascribed to the abundant active sites/defects in the amorphous framework and promotion of activity through cobalt doping. Furthermore, the superhydrophilicity and superaerophobicity of micro-/nanostructured CoMoSx /NF promoted mass transfer by facilitating access of electrolytes and ensuring fast release of gas bubbles. By employing CoMoSx /NF as bifunctional electrocatalysts, the overall water splitting device delivered a current density of 500 mA cm-2 at a low voltage of 1.89 V and maintained its activity without decay for 100 h.

The development of function-integrated catalysts to enable scalable and efficient biomass valorization is an important topic. Here, a stepwise methodology was developed to fabricate novel supported Au–Pd bimetallic catalysts featuring immobilized well-defined on-surface nanoarchitectures (Pd∧Au). This was achieved by an atomic decoration of a trace amount of Pd (Pd/Au molar ratio of 0.01–0.02) on the surface of 2 nm Au nanoparticle (NP, 0.86 wt %) preanchored to titania. Benefiting from their unique structural merits and the cooperative interplay among the selective hydrogenation activity furnished by the ultrasmall Pd∧Au NPs and prominent Lewis acidity endowed by TiO2, Pd0.02∧Au/TiO2 exhibits excellent activity with 100% conversion and over 90% selectivity and stability (turnover number up to 48 300) toward controlled ring-opening conversion of 5-hydroxymethylfurfural and related furanic compounds to the corresponding di- and triketone-type products under mild conditions (120 °C, 10 bar of H2). The resul...

Electrochemical CO2 reduction reaction (ECO2RR) is an important route for global carbon abatement. However, a comprehensive picture of the structure evolution of metal active sites is currently lacked in ECO2RR. Here, we present the first full view of Ni single-atom catalyst for ECO2RR over a broad potential range. Comprehensive X-ray absorption spectroscopy (XAS) analyses confirmed the Ni coordinated with pyrrole nitrogen in the form of Ni-N4 attached with an axial O2 ligand. Operando XAS revealed the precise structure of the Ni single-atom catalyst that dynamically changes with the shift of applied potentials. Such changes ultimately contributed to the CO selectivity variation ranging from 20%-99%. Interestingly, the Ni center was found to move toward the N4 plane during the ECO2RR, which played a crucial role of reaching near-unity CO selectivity. Together with theoretical calculations, a clear quantitative correlation between the dynamic configuration and the catalytic properties was established.

The effective activation and utilization of O

The greatest challenge for lithium-sulfur (Li-S) batteries application is the development of cathode hosts to address the low conductivity, huge volume change, and shuttling effect of sulfur or lithium polysulfides (LiPs). Herein, we demonstrate a composite host to circumvent these problems by confining sub-nanometric manganous oxide clusters (MOCs) in nitrogen doped mesoporous carbon nanosheets. The atomic structure of MOCs is well-characterized and optimized via the extended X-ray absorption fine structure analysis and density functional theory (DFT) calculations. Benefiting from the unique design, the assembled Li-S battery displays remarkable electrochemical performances including a high reversible capacity (990 mAh g-1 after 100 cycles at 0.2 A g-1) and a superior cycle life (60% retention over 250 cycles at 2 A g-1). Both the experimental results and DFT calculations demonstrate that the well-dispersed MOCs could significantly promote the chemisorption of LiPs, thus greatly improving the capacity and rate performance.

Isolated cobalt single atoms with a high loading of 5.9 wt% are generated through an in situ preparation strategy., Single-atom catalysts (SACs) have shown great potential in a wide variety of chemical reactions and become the most active new frontier in catalysis due to the maximum efficiency of metal atom use. The key obstacle in preparing SAs lies in the development of appropriate supports that can avoid aggregation or sintering during synthetic procedures. As such, achieving high loadings of isolated SAs is nontrivial and challenging. Conventional methods usually afford the formation of SAs with extremely low loadings (less than 1.5 wt%). In this work, a new in situ preparation strategy that enables the synthesis of isolated cobalt (Co) SAs with an exceptionally high metal loading, up to 5.9 wt%, is developed. The approach is based on a simple one-step pyrolysis of a nitrogen-enriched molecular carbon precursor (1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile) and CoCl2. Furthermore, due to the successful electron transfer from carbon nitride to the isolated Co SAs, we demonstrate a high-performance photocatalytic H2 production using Co SAs as a co-catalyst, and the evolution rate is measured to be 1180 μmol g–1 h–1. We anticipate that this new study will inspire the discovery of more isolated SACs with high metal loadings, evidently advancing the development of this emerging type of advanced catalysts.