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The application of Li-rich layered oxides is hindered by their dramatic capacity and voltage decay on cycling. This work comprehensively studies the mechanistic behaviour of cobalt-free Li1.2Ni0.2Mn0.6O2 and demonstrates the positive impact of two-phase Ru doping. A mechanistic transition from the monoclinic to the hexagonal behaviour is found for the structural evolution of Li1.2Ni0.2Mn0.6O2, and the improvement mechanism of Ru doping is understood using the combination of in operando and post-mortem synchrotron analyses. The two-phase Ru doping improves the structural reversibility in the first cycle and restrains structural degradation during cycling by stabilizing oxygen (O2−) redox and reducing Mn reduction, thus enabling high structural stability, an extraordinarily stable voltage (decay rate 1.2Ni0.2Mn0.6O2 sheds light on the selective doping strategy and rational materials design for better-performance Li-rich layered oxides.

Environmental context Toxicity and mobility of antimony and arsenic in aqueous systems are largely determined by their speciation and redox chemistry. In a highly contaminated freshwater system, one antimony species (dissolved SbV) dominated, while dissolved arsenic was more responsive to environmental conditions. Arsenic (as AsV) increased significantly during a drought period; this increase in As mobility presents a threat for first flush events and water contamination in a changing climate. Abstract Aqueous and solid-state antimony (Sb) and arsenic (As) speciation is assessed in an Australian freshwater system contaminated by mining of primary sulfide minerals. The study aims to understand metalloid transformation and mobilisation in the system, and coincides with a severe drought providing the opportunity to examine the influence of extreme low-flow conditions. X-ray absorption spectra identified only SbV in

Ammonia (NH3) is a basic chemical feedstock for the production of fertilizers and pharmaceuticals, and it emerges as a new hydrogen energy carrier for renewable energy sources such as solar and wind power. A photoelectrochemical nitrogen reduction reaction (PEC NRR) under mild operating conditions represents a potentially green and convenient approach for the synthesis of NH3. However, a generally applicable PEC NRR featuring a high NH3 yield and a satisfactory conversion efficiency remains elusive. Herein, we report on a simple and effective electrochemistry-assisted strategy to enhance the PEC fixation of N2 to NH3. Using this strategy, we harness a steel-based cathode-assisted Au/SiO2/Si photocathode to seamlessly combine two critical reaction steps-N2 activation and hydrogenation-to realize an NH3 yield rate of 22.0 μg·cm-2·h-1 and a faradic efficiency of 23.7% at-0.2 V versus a reversible hydrogen electrode under one sun illumination. We also provide an accessible reaction setup to avoid the disturbance of a contamination by air, human breath, and N2 stream, leading to a reliable production of NH3 by the PEC NRR. An operando characterization and a theoretical calculation uncover the active sites and reaction mechanism of the whole system for an electrochemistry-assisted PEC NRR. This work demonstrates the capability of an electrochemistry-assisted excitation in PEC NRR, and it introduces a new design concept for addressing pertinent challenges in photoelectrochemical and other chemical fields.

Dual-atom catalysts (DACs) have become an emerging platform to provide more flexible active sites for electrocatalytic reactions with multi-electron/proton transfer, such as CO

Not only high efficiency but also high selectivity of the electrocatalysts is crucial for high-performance, low-cost, and sustainable energy storage applications. Herein, we systematically investigate the edge effect of carbon-supported single-atom catalysts (SACs) on oxygen reduction reaction (ORR) pathways (two-electron (2 e

Single-atom catalysts (SACs) exhibit unparalleled atomic utilization and catalytic efficiency, yet it is challenging to modulate SACs with highly dispersed single-atoms, mesopores, and well-regulated coordination environment simultaneously and ultimately maximize their catalytic efficiency. Here, a generalized strategy to construct highly active ferric-centered SACs (Fe-SACs) is developed successfully via a biomineralization strategy that enables the homogeneous encapsulation of metalloproteins within metal-organic frameworks (MOFs) followed by pyrolysis. The results demonstrate that the constructed metalloprotein-MOF-templated Fe-SACs achieve up to 23-fold and 47-fold higher activity compared to those using metal ions as the single-atom source and those with large mesopores induced by Zn evaporation, respectively, as well as up to a 25-fold and 1900-fold higher catalytic efficiency compared to natural enzymes and natural-enzyme-immobilized MOFs. Furthermore, this strategy can be generalized to a variety of metal-containing metalloproteins and enzymes. The enhanced catalytic activity of Fe-SACs benefits from the highly dispersed atoms, mesopores, as well as the regulated coordination environment of single-atom active sites induced by metalloproteins. Furthermore, the developed Fe-SACs act as an excellent and effective therapeutic platform for suppressing tumor cell growth. This work advances the development of highly efficient SACs using metalloproteins-MOFs as a template with diverse biotechnological applications.

The first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron, Australia, is presented. In this experiment X-ray mass attenuation coefficients are measured across an energy range including the zinc K-absorption edge and X-ray absorption fine structure (XAFS). These high-accuracy measurements are recorded at 496 energies from 8.51 keV to 11.59 keV. The XERT protocol dictates that systematic errors due to dark current nonlinearities, correction for blank measurements, full-foil mapping to characterize the absolute value of attenuation, scattering, harmonics and roughness are measured over an extended range of experimental parameter space. This results in data for better analysis, culminating in measurement of mass attenuation coefficients across the zinc K-edge to 0.023–0.036% accuracy. Dark current corrections are energy- and structure-dependent and the magnitude of correction reached 57% for thicker samples but was still large and significant for thin samples. Blank measurements scaled thin foil attenuation coefficients by 60–500%; and up to 90% even for thicker foils. Full-foil mapping and characterization corrected discrepancies between foils of up to 20%, rendering the possibility of absolute measurements of attenuation. Fluorescence scattering was also a major correction. Harmonics, roughness and bandwidth were explored. The energy was calibrated using standard reference foils. These results represent the most extensive and accurate measurements of zinc which enable investigations of discrepancies between current theory and experiments. This work was almost fully automated from this first experiment at the Australian Synchrotron, greatly increasing the possibility for large-scale studies using XERT.

The most accurate measurements of the mass attenuation coefficient for metals at low temperature for the zinc K-edge from 9.5 keV to 11.5 keV at temperatures of 10 K, 50 K, 100 K and 150 K using the hybrid technique are reported. This is the first time transition metal X-ray absorption fine structure (XAFS) has been studied using the hybrid technique and at low temperatures. This is also the first hybrid-like experiment at the Australian Synchrotron. The measured transmission and fluorescence XAFS spectra are compared and benchmarked against each other with detailed systematic analyses. A recent method for modelling self-absorption in fluorescence has been adapted and applied to a solid sample. The XAFS spectra are analysed using eFEFFIT to provide a robust measurement of the evolution of nanostructure, including such properties as net thermal expansion and mean-square relative displacement. This work investigates crystal dynamics, nanostructural evolution and the results of using the Debye and Einstein models to determine atomic positions. Accuracies achieved, when compared with the literature, exceed those achieved by both relative and differential XAFS, and represent a state-of-the-art for future structural investigations. Bond length uncertainties are of the order of 20–40 fm.

Oxides composed of an oxygen framework and interstitial cations are promising cathode materials for lithium-ion batteries. However, the instability of the oxygen framework under harsh operating conditions results in fast battery capacity decay, due to the weak orbital interactions between cations and oxygen (mainly 3d–2p interaction). Here, a robust and endurable oxygen framework is created by introducing strong 4s–2p orbital hybridization into the structure using LiNi0.5Mn1.5O4 oxide as an example. The modified oxide delivers extraordinarily stable battery performance, achieving 71.4 % capacity retention after 2000 cycles at 1 C. This work shows that an orbital-level understanding can be leveraged to engineer high structural stability of the anion oxygen framework of oxides. Moreover, the similarity of the oxygen lattice between oxide electrodes makes this approach extendable to other electrodes, with orbital-focused engineering a new avenue for the fundamental modification of battery materials.

Furfural is regarded as one of the most promising bio-based feedstocks in the bio-refinery industry. Selective hydrogenation of the carbonyl bond in furfural plays a vital role in its conversion to downstream products. Electrochemical hydrogenation (ECH) method provides a green and sustainable way for this reaction. Yet, it still suffers from harsh pH conditions and low selectivity for highly reduced products, such as 2-methylfuran. In this study, high faradaic efficiencies of over 90% for furfuryl alcohol and 60% for 2-methylfuran were obtained in a near-neutral environment (pH = 5) at −0.75 V and −0.90 V vs. the reversible hydrogen electrode, respectively. The key to this success is the integration of single atom copper active sites and the oxophilic phosphorus dopants in a single catalyst. Single atom Cu sites are found to be the active centers for this reaction and decreasing the size of Cu sites to a single atom enhances the efficiencies of the ECH reactions by suppressing the competing hydrogen evolution reaction. Phosphorus doping facilitates furfural hydrogenation to 2-methylfuran via a sequential two-step reduction process. This study opens up possibilities for the selective electrochemical hydrogenation of furfural to 2-methylfuran under mild conditions.

The development of a highly efficient strategy for the activation of the C–H bond in hydrocarbons is one of the most challenging tasks facing the chemical industries. The synthesis of novel catalysts with atomically dispersed active centers is highly desirable to achieve the maximized atom efficiency. Here we report the controllable preparation of a Co-based single-atom catalyst anchored on a graphitic carbon nitride support (SACo@g-C3N4) with 3.17 wt% Co content, which is successfully applied for the selective oxidation of ethylbenzene (EB) to derive acetophenone (AcPO) via the activated peroxymonosulfate (PMS) oxidant. The Co atoms are chemically bonded with the N atoms of g-C3N4 and present exceptional stability and reusability to resist the applied acidic-oxidative environment. Both the EB conversion and AcPO selectivity were over 95% in this highly selective SACo@g-C3N4/PMS system under mild reaction conditions. The selective conversion of EB into AcPO is attributed to the oxidative radicals generated from the decomposition of PMS molecules via the electron transfer between Co atoms and PMS. Sulfate radicals (SO4˙−) make a greater contribution than others to activate the C–H bond in EB oxidation. This work uncovers a facile and scalable approach for the synthesis of a robust Co-based single atom catalyst (SAC) on a g-C3N4 support and unveils its potential in the oxidation of hydrocarbons via a highly efficient and environmentally benign PMS activation.

Herein, the series Sc2WxMo3−xO12 (0 ≤ x ≤ 3) is synthesised and the structure and electrochemical performance in alkali-ion batteries is characterised. The structures remain in the orthorhombic Pnca space group for the whole series with the lattice parameters increasing approximately linearly from {a = 9.6336(2) A, b = 13.2406(3) A, c = 9.5413(2) A} in Sc2Mo3O12 to {a = 9.6735(2) A, b = 13.3218(3) A, c = 9.5811(2) A} in Sc2W3O12. Discharge against Li delivers a high initial discharge capacity of 1200 mA h g−1 for Sc2Mo3O12 with a reversible capacity of about 150 mA h g−1 after 100 cycles. Meanwhile the increase of W content reduces both the initial and overall capacities for all lithium, sodium and potassium half cells. The initial discharge capacity for Sc2W3O12 against lithium is only about 700 mA h g−1 with a reversible capacity of about 100 mA h g−1 after 100 cycles. For all sodium and potassium half cells across the series, the capacities drop dramatically after a few cycles and the reversible capacities are low, below 50 mA h g−1. Structurally, the fully potassium discharged Sc2Mo3O12 partially transforms into a new P space group KMo4O6 phase, while the crystallinity decreases in both fully lithium and sodium discharged Sc2Mo3O12. For Sc2W3O12, only fully potassium discharged Sc2W3O12 shows a decrease in crystallinity, while the fully lithium and sodium discharged Sc2W3O12 appears to become amorphous (or particles are too small to be examined with X-ray diffraction). X-ray absorption spectroscopy demonstrates that the Mo oxidation state changes with different type and amount of alkali-ion discharge. This work illustrates the influence of composition on the electrochemical performance in this family of compounds.

Nickel-based catalysts are most commonly used in industrial alkaline water electrolysis. However, it remains a great challenge to address the sluggish reaction kinetics and severe deactivation problems of hydrogen evolution reaction (HER). Here, we show a Cu-doped Ni catalyst implanted with Ni-O-VOx sites (Ni(Cu)VOx) for alkaline HER. The optimal Ni(Cu)VOx electrode exhibits a near-zero onset overpotential and low overpotential of 21 mV to deliver –10 mA cm−2, which is comparable to benchmark Pt/C catalyst. Evidence for the formation of Ni-O-VOx sites in Ni(Cu)VOx is established by systematic X-ray absorption spectroscopy studies. The VOx can cause a substantial dampening of Ni lattice and create an enlarged electrochemically active surface area. First-principles calculations support that the Ni-O-VOx sites are superactive and can promote the charge redistribution from Ni to VOx, which greatly weakens the H-adsorption and H2 release free energy over Ni. This endows the Ni(Cu)VOx electrode high HER activity and long-term durability., Producing H2 from water using electricity and earth-abundant elements is necessary for worldwide renewable fuel production, yet most electrocatalysts have sluggish activities or poor stabilities. Here, authors show vanadium oxide modified copper-doped nickel to enable active and durable H2 evolution.

Single-atom catalysts (SACs) have attracted much attentions due to the advantages of high catalysis efficiency and selectivity. However, the controllable and efficient synthesis of SACs remains a significant challenge. Herein, we report a controlled one-pot synthesis of nickel single atoms embedded on nitrogen-doped carbon nanotubes (NiSA−N−CNT) and nitrogen-doped graphene (NiSA−N−G). The formation of NiSA−N−CNT is due to the solid-to-solid rolling up mechanism during the high temperature pyrolysis at 800 °C from the stacked and layered Ni-doped g-CN, g-CN−Ni structure to a tubular CNT structure. Addition of citric acid introduces an amorphous carbon source on the layered g-CN−Ni and after annealing at the same temperature of 800 °C, instead of formation of NiSA−N−CNT, Ni single atoms embedded in planar graphene type supports, NiSA−N−G were obtained. The density functional theory (DFT) calculation indicates the introduction of amorphous carbon source substantially reduces the structure fluctuation or curvature of layered g-CN-Ni intermediate products, thus interrupting the solid-to-solid rolling process and leading to the formation of planar graphene type supports for Ni single atoms. The as-synthesized NiSA−N−G with Ni atomic loading of ∼6 wt% catalysts shows a better activity and stability for the CO reduction reaction (CORR) than NiSA−N−CNT with Ni atomic loading of ∼15 wt% due to the open and exposed Ni single atom active sites in NiSA−N−G. This study demonstrates for the first time the feasibility in the control of the microstructure of carbon supports in the synthesis of SACs.

Spinel LiNi0.5 Mn1.5 O4 (LNMO) is a promising cathode candidate for the next-generation high energy-density lithium-ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site-selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd 3 ‾ m structure. This site-selective doping not only suppresses unfavorable two-phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg-doped LNMOs exhibit extraordinarily stable electrochemical performance in both half-cells and prototype full-batteries with novel TiNb2 O7 counter-electrodes. This work pioneers an atomic-doping engineering strategy for electrode materials that could be extended to other energy materials to create high-performance devices.

Core/shell nanocrystals with a graded interface between core and shell exhibit improved optoelectronic properties compared with particles with an abrupt, sharp interface. Material gradients mitigate interfacial defects and define the shape of the confinement potential. So far, few works exist that allow to quantify the width of the gradient. In this study, ZnSe/CdS nanocrystals with graded shells made at different temperatures are characterized using extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies. The average coordination number of the probed element with respect to the two possible counterions is fit to a simple, geometric model. It is shown that at the lower temperature limit for shell growth (260 °C), substantial interfacial alloying can be attributed mainly to cation migration. At higher temperature (290 °C), strain minimization leads to atomic ordering of the metal ions and an anomalously low degree of phase mixing.

A sodium-rich vanadium compound, Na4V2O7, is investigated as a cathode material for sodium-ion batteries, which delivers a high reversible capacity of 194 mA h g−1 after activating to 4.7 V. By limiting the cut-off voltage to 4.4 V, a good capacity retention of 93% after 50 cycles is achieved. The material exhibits a negligible volume variation of 1.04% during Na+ (de-)intercalation, demonstrating that Na4V2O7 is structurally-stable.