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Gold-based co-catalysts are a promising class of materials with potential applications in photocatalytic H 2 O 2 production. However, current approaches with Au co-catalysts show limited H 2 O 2 production due to intrinsically weak O 2 adsorption at the Au site. We report an approach to strengthen O 2 adsorption at Au sites, and to improve H 2 O 2 production, through the formation of electron-deficient Au δ+ sites by modifying the electronic structure. In this case, we report the synthesis of TiO 2 /MoS x -Au, following selective deposition of Au onto a MoS x surface which is then further anchored onto TiO 2 . We further show that the catalyst achieves a significantly increased H 2 O 2 production rate of 30.44 mmol g −1  h −1 in O 2 -saturated solution containing ethanol. Density functional theory calculations and X-ray photoelectron spectroscopy analysis reveal that the MoS x mediator induces the formation of electron-deficient Au δ+ sites thereby decreasing the antibonding-orbital occupancy of Au-O ads and subsequently enhancing O 2 adsorption. This strategy may be useful for rationally designing the electronic structure of catalyst surfaces to facilitate artificial photosynthesis. Photocatalytic H 2 O 2 production using Au is hindered by its inherently weak O 2 adsorption. Herein, the authors modify the electronic structure of Au with MoS x to form electron deficient Au sites to promote O 2 adsorption and H 2 O 2 production.

Photocatalytic hybrid carbon nanotubes (CNTs)–mediated Ag-CuBi 2 O 4 /Bi 2 WO 6 photocatalyst was fabricated using a hydrothermal technique to effectively eliminate organic pollutants from wastewater. The as-prepared samples were characterized via Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction patterns (XRD), high-resolution transmission electron microscope (HR-TEM), UV–vis Diffuse Reflectance spectrum (UV–Vis DRS), and photoluminescence (PL) studies. The photocatalytic performance of fabricated pristine and hybrid composites was examined by photo-degradation of toxic dye viz. Rhodamine B (RhB) under visible light. Photo-degradation results revealed that the fabricated Ag-CuBi 2 O 4 /CNTs/Bi 2 WO 6 semiconductor photocatalyst followed pseudo-first-order kinetics and displayed a higher photocatalytic rate, which was found to be approximately 3.33 and 2.35 times higher than the pristine CuBi 2 O 4 and Bi 2 WO 6 semiconductor photocatalyst, respectively. Re-cyclic results demonstrated that the formed composite owns excellent stability, even after five consecutive cycles. As per the matched Fermi level of CNTs in between Ag-CuBi 2 O 4 and Bi 2 WO 6 , carbon nanotubes severed as electron transfer-bridge, Ag doping on CuBi 2 O 4 surface successfully increased photon absorption all across CuBi 2 O 4 surface. Also, it hindered the assimilation of photoinduced electron–hole pairs. The increased photocatalytic efficiency is contributed to the uniform dispersion of photo-generated electron–hole pairs via the construction of an S-scheme system. ROS trapping and ESR experiments suggested that (∙OH) and (O 2 − ∙) were the main radical species for enhanced photo-degradation of RhB dye. The current investigation, from our perspective, highlights the new insights for the fabrication of practical CNTs-mediated S-scheme–based semiconductor photocatalyst for the resolution of environmental issues based on practical considerations.

Transition metal chalcogenides have been identified as low-cost and efficient electrocatalysts to promote the hydrogen evolution reaction in alkaline media. However, the identification of active sites and the underlying catalytic mechanism remain elusive. In this work, we employ operando X-ray absorption spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy to elucidate that NiS undergoes an in-situ phase transition to an intimately mixed phase of Ni 3 S 2 and NiO, generating highly active synergistic dual sites at the Ni 3 S 2 /NiO interface. The interfacial Ni is the active site for water dissociation and OH* adsorption while the interfacial S acts as the active site for H* adsorption and H 2 evolution. Accordingly, the in-situ formation of Ni 3 S 2 /NiO interfaces enables NiS electrocatalysts to achieve an overpotential of only 95 ± 8 mV at a current density of 10 mA cm −2 . Our work highlighted that the chemistry of transition metal chalcogenides is highly dynamic, and a careful control of the working conditions may lead to the in-situ formation of catalytic species that boost their catalytic performance. Transition metal chalcogenides are effective and economical electrocatalysts for the hydrogen evolution reaction in alkaline media, yet active sites and catalytic mechanisms remain unclear. Here the authors use operando spectroscopy to study the in-situ conversion of NiS to highly active Ni 3 S 2 /NiO dual-site catalysts for the alkaline hydrogen evolution reaction.

Preventing the deactivation of noble metal-based catalysts due to self-oxidation and poisonous adsorption is a significant challenge in organic electro-oxidation. In this study, we employ a pulsed potential electrolysis strategy for the selective electrocatalytic oxidation of glycerol to glyceric acid over a Pt-based catalyst. In situ Fourier-transform infrared spectroscopy, quasi-in situ X-ray photoelectron spectroscopy, and finite element simulations reveal that the pulsed potential could tailor the catalyst’s oxidation and surface micro-environment. This prevents the overaccumulation of poisoning intermediate species and frees up active sites for the re-adsorption of OH adsorbate and glycerol. The pulsed potential electrolysis strategy results in a higher glyceric acid selectivity (81.8%) than constant-potential electrocatalysis with 0.7 V RHE (37.8%). This work offers an efficient strategy to mitigate the deactivation of noble metal-based electrocatalysts. Mitigating the deactivation of noble metal-based catalysts caused by self-oxidation and toxic adsorption poses a considerable challenge in organic electro-oxidation. This study addresses the issue by employing a pulsed potential electrolysis approach to selectively electrocatalyze the oxidation of glycerol to glyceric acid using a Pt-based catalyst.

Beamline 13 of the Photon Factory has been in operation since 2010 as a vacuum ultraviolet and soft X‐ray undulator beamline for X‐ray photoelectron spectroscopy (XPS), X‐ray absorption spectroscopy (XAS), and angle‐resolved photoelectron spectroscopy (ARPES) experiments. The beamline and the end‐station at branch B have been recently upgraded, enabling microscopic XPS, XAS, and ARPES measurements to be performed. In 2015, a planar undulator insertion device was replaced with an APPLE‐II (advanced planar polarized light emitter II) undulator. This replacement allows use of linear, circular, and elliptical polarized light between 48 and 2000 eV with photon intensities of 109–1013 photons s−1. For microscopic measurements, a toroidal post‐mirror was renewed to have more focused beam with profile sizes of 78 µm (horizontal) × 15 µm (vertical) and 84 µm × 11 µm at photon energies of 100 and 400 eV, respectively. A high‐precision sample manipulator composed of an XYZ translator, a rotary feedthrough, and a newly developed goniometer, which is essential for microscopic measurements, has been used to control a sample specimen in six degrees of freedom, i.e. translation in the X, Y, and Z directions and rotation in the polar, azimuthal, and tilt directions. To demonstrate the performance of the focused beams, one‐ and two‐dimensional XPS and XAS scan measurements of a copper grid have been performed. It was indicated from analysis of XPS and XAS intensity maps that the actual spatial resolution can be determined by the beam size. Beamline BL‐13B of the Photon Factory and the end‐station have been upgraded, enabling microscopic XPS, XAS, and ARPES measurements with a spatial resolution that is comparable with the size of the focused beam. Beam profile evaluation and experimental demonstration of microscopic measurements are presented.

SignificanceCombining ambient pressure X-ray photoelectron spectroscopy experiments and quantum mechanical density functional theory calculations, this work reveals the essential first step for activating CO2 on a Cu surface, in particular, highlighting the importance of copper suboxide and the critical role of water. These findings provide the quintessential information needed to guide the future design of improved catalysts. A national priority is to convert CO2 into high-value chemical products such as liquid fuels. Because current electrocatalysts are not adequate, we aim to discover new catalysts by obtaining a detailed understanding of the initial steps of CO2 electroreduction on copper surfaces, the best current catalysts. Using ambient pressure X-ray photoelectron spectroscopy interpreted with quantum mechanical prediction of the structures and free energies, we show that the presence of a thin suboxide structure below the copper surface is essential to bind the CO2 in the physisorbed configuration at 298 K, and we show that this suboxide is essential for converting to the chemisorbed CO2 in the presence of water as the first step toward CO2 reduction products such as formate and CO. This optimum suboxide leads to both neutral and charged Cu surface sites, providing fresh insights into how to design improved carbon dioxide reduction catalysts.

Graded bulk-heterojunction (G-BHJ) with well-defined vertical phase separation has potential to surpass classical BHJ in organic solar cells (OSCs). In this work, an effective G-BHJ strategy via nonhalogenated solvent sequential deposition is demonstrated using nonfullerene acceptor (NFA) OSCs. Spin-coated G-BHJ OSCs deliver an outstanding 17.48% power conversion efficiency (PCE). Depth-profiling X-ray photoelectron spectroscopy (DP-XPS) and angle-dependent grazing incidence X-ray diffraction (GI-XRD) techniques enable the visualization of polymer/NFA composition and crystallinity gradient distributions, which benefit charge transport, and enable outstanding thick OSC PCEs (16.25% for 300 nm, 14.37% for 500 nm), which are among the highest reported. Moreover, the nonhalogenated solvent enabled G-BHJ OSC via open-air blade coating and achieved a record 16.77% PCE. The blade-coated G-BHJ has drastically different D-A crystallization kinetics, which suppresses the excessive aggregation induced unfavorable phase separation in BHJ. All these make G-BHJ a feasible and promising strategy towards highly efficient, eco- and manufacture friendly OSCs. Graded bulk-heterojunction organic solar cell with well-defined vertical phase separation has the potential to surpass the classical counterpart, thus the optimisation of this structure is crucial. Here, the authors reveal solvent selection strategies for optimising morphology of the structure, enabling efficient, eco-friendly, and scalable solar cells.

Herein, ruthenium (Ru) and iridium (Ir) are introduced to tailor the atomic and electronic structure of self-supported nickel-vanadium (NiV) layered double hydroxide to accelerate water splitting kinetics, and the origin of high hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities are analyzed at atomic level. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectroscopy studies reveal synergistic electronic interactions among Ni, V, and Ru (Ir) cations. Raman spectra and Fourier and wavelet transform analyses of the extended X-ray absorption fine structure indicate modulated local coordination environments around the Ni and V cations, and the existence of V vacancies. The Debye–Waller factor suggests a severely distorted octahedral V environment caused by the incorporation of Ru and Ir. Theoretical calculations further confirm that Ru or Ir doping could optimize the adsorption energy of intermediates in the Volmer and Heyrovsky steps for HER and accelerate the whole kinetic process for OER. While water-splitting affords a renewable means to store energy, expensive catalysts are often required to achieve high performances. Here, authors modulate nickel-vanadium double hydroxide properties by noble-metal doping to accelerate electrocatalytic water splitting kinetics.

In this study, different types of magnetic biochar nanocomposites were synthesized using the co-precipitation method. Two biochar materials, namely, sewage sludge biochar and woodchips biochar, were prepared at two different temperatures, viz., 450 and 700 °C. These biochars were further modified with magnetic nanoparticles (Fe 3 O 4 ). The modified biochar nanocomposites were characterized using field emission–scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), SQUID analysis, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). The potential of prepared adsorbents was examined for the removal of hexavalent chromium (Cr(VI)) and Acid orange 7 (AO7) dye from water as a function of various parameters, namely, contact time, pH of solution, amount of adsorbents, and initial concentrations of adsorbates. Various kinetic and isotherm models were tested to discuss and interpret the adsorption mechanisms. The maximum adsorption capacities of modified biochars were found as 80.96 and 110.27 mg g -1 for Cr(VI) and AO7, respectively. Magnetic biochars showed high pollutant removal efficiency after 5 cycles of adsorption/desorption. The results of this study revealed that the prepared adsorbents can be successfully used for multiple cycles to remove Cr(VI) and AO7 from water. Graphical Abstract

The large-scale conversion of N 2 and H 2 into NH 3 (refs.  1 , 2 ) over Fe and Ru catalysts 3 for fertilizer production occurs through the Haber–Bosch process, which has been considered the most important scientific invention of the twentieth century 4 . The active component of the catalyst enabling the conversion was variously considered to be the oxide 5 , nitride 2 , metallic phase or surface nitride 6 , and the rate-limiting step has been associated with N 2 dissociation 7 – 9 , reaction of the adsorbed nitrogen 10 and also NH 3 desorption 11 . This range of views reflects that the Haber–Bosch process operates at high temperatures and pressures, whereas surface-sensitive techniques that might differentiate between different mechanistic proposals require vacuum conditions. Mechanistic studies have accordingly long been limited to theoretical calculations 12 . Here we use X-ray photoelectron spectroscopy—capable of revealing the chemical state of catalytic surfaces and recently adapted to operando investigations 13 of methanol 14 and Fischer–Tropsch synthesis 15 —to determine the surface composition of Fe and Ru catalysts during NH 3 production at pressures up to 1 bar and temperatures as high as 723 K. We find that, although flat and stepped Fe surfaces and Ru single-crystal surfaces all remain metallic, the latter are almost adsorbate free, whereas Fe catalysts retain a small amount of adsorbed N and develop at lower temperatures high amine (NH x ) coverages on the stepped surfaces. These observations indicate that the rate-limiting step on Ru is always N 2 dissociation. On Fe catalysts, by contrast and as predicted by theory 16 , hydrogenation of adsorbed N atoms is less efficient to the extent that the rate-limiting step switches following temperature lowering from N 2 dissociation to the hydrogenation of surface species. Using X-ray photoelectron spectroscopy, the surface composition of iron and ruthenium catalysts during ammonia synthesis at pressures up to 1 bar and temperatures as high as 723 K can be revealed.