devices to allow energy release at night and for continuous supply under low wind conditions. The most prevalent type of secondary energy storage uses lithiumion batteries (LIBs), that possess high energy density and long cycle life and have brought about a remarkable technical revolution for portable electronics, vehicles, and many other aspects in daily life. [1] However, considering the growing cost of the limited lithium resources and safety concerns derived from intrinsic chemical activity of metallic lithium and its combustible ester electrolytes, aqueous rechargeable batteries have been recently spotlighted as promising alternatives especially for utilization of large-scale energy storage stations. [2] Among them, aqueous zinc-ion batteries (AZIBs) have gained exceptional interest in aqueous systems due to the beneficial physicochemical properties of zinc, that is, i) a high theoretical volumetric capacity around 5585 mAh cm −3 of a metallic zinc anode compared with 2061 mAh cm −3 and 1129 mAh cm −3 for lithium and sodium anodes, respectively; ii) low redox potential of −0.762 V versus standard hydrogen electrode, and iii) electrochemical stability of metallic zinc in its sulfate solutions at near neutral or slightly acidic aqueous electrolyte providing the batteries with safe, costeffective, and environment-friendly characteristics. [3][4][5][6] Cost-effective and environmentally-friendly aqueous zinc-ion batteries (AZIBs) exhibit tremendous potential for application in grid-scale energy storage systems but are limited by suitable cathode materials. Hydrated vanadium bronzes have gained significant attention for AZIBs and can be produced with a range of different pre-intercalated ions, allowing their properties to be optimized. However, gaining a detailed understanding of the energy storage mechanisms within these cathode materials remains a great challenge due to their complex crystallographic frameworks, limiting rational design from the perspective of enhanced Zn 2+ diffusion over multiple length scales. Herein, a new class of hydrated porous δ-Ni 0.25 V 2 O 5 .nH 2 O nanoribbons for use as an AZIB cathode is reported. The cathode delivers reversibility showing 402 mAh g −1 at 0.2 A g −1 and a capacity retention of 98% over 1200 cycles at 5 A g −1 . A detailed investigation using experimental and computational approaches reveal that the host "δ" vanadate lattice has favorable Zn 2+ diffusion properties, arising from the atomic-level structure of the well-defined lattice channels. Furthermore, the microstructure of the as-prepared cathodes is examined using multi-length scale X-ray computed tomography for the first time in AZIBs and the effective diffusion coefficient is obtained by imagebased modeling, illustrating favorable porosity and satisfactory tortuosity.

Nanoparticle (NP) mediated photothermal effect shows great potential as a noninvasive method for cancer therapy treatment, but the development of photothermal agents with high photothermal conversion efficiency, small size and good biocompatibility is still a big challenge. Herein, we report Pd NPs with a porous structure exhibiting enhanced near infrared (NIR) absorption as compared to Pd nanocubes with a similar size (almost two-fold enhancement with a molar extinction coefficient of 6.3 × 10(7) M(-1) cm(-1)), and the porous Pd NPs display monotonically rising absorbance from NIR to UV-Vis region. When dispersed in water and illuminated with an 808 nm laser, the porous Pd NPs give a photothermal conversion efficiency as high as 93.4%, which is comparable to the efficiency of Au nanorods we synthesized (98.6%). As the porous Pd NPs show broadband NIR absorption (650-1200 nm), this allows us to choose multiple laser wavelengths for photothermal therapy. In vitro photothermal heating of HeLa cells in the presence of porous Pd NPs leads to 100% cell death under 808 nm laser irradiation (8 W cm(-2), 4 min). For photothermal heating using 730 nm laser, 70% of HeLa cells were killed after 4 min irradiation at a relative low power density of 6 W cm(-2). These results demonstrated that the porous Pd nanostructure is an attractive photothermal agent for cancer therapy.

Iridium and ruthenium and their oxides/hydroxides are the best candidates for the oxygen evolution reaction under harsh acidic conditions owing to the low overpotentials observed for Ru- and Ir-based anodes and the high corrosion resistance of Ir-oxides. Herein, by means of cutting edge operando surface and bulk sensitive X-ray spectroscopy techniques, specifically designed electrode nanofabrication and ab initio DFT calculations, we were able to reveal the electronic structure of the active IrO x centers (i.e., oxidation state) during electrocatalytic oxidation of water in the surface and bulk of high-performance Ir-based catalysts. We found the oxygen evolution reaction is controlled by the formation of empty Ir 5d states in the surface ascribed to the formation of formally Ir V species leading to the appearance of electron-deficient oxygen species bound to single iridium atoms (μ 1 -O and μ 1 -OH) that are responsible for water activation and oxidation. Oxygen bound to three iridium centers (μ 3 -O) remains the dominant species in the bulk but do not participate directly in the electrocatalytic reaction, suggesting bulk oxidation is limited. In addition a high coverage of a μ 1 -OO (peroxo) species during the OER is excluded. Moreover, we provide the first photoelectron spectroscopic evidence in bulk electrolyte that the higher surface-to-bulk ratio in thinner electrodes enhances the material usage involving the precipitation of a significant part of the electrode surface and near-surface active species.

Understanding and tuning the catalytic properties of metals atomically dispersed on oxides are major stepping-stones towards a rational development of single-atom catalysts (SACs). Beyond individual showcase studies, the design and synthesis of structurally regular series of SACs opens the door to systematic experimental investigations of performance as a function of metal identity. Herein, a series of single-atom catalysts based on various 4d (Ru, Rh, Pd) and 5d (Ir, Pt) transition metals has been synthesized on a common MgO carrier. Complementary experimental (X-ray absorption spectroscopy) and theoretical (Density Functional Theory) studies reveal that, regardless of the metal identity, metal cations occupy preferably octahedral coordination MgO lattice positions under step-edges, hence highly confined by the oxide support. Upon exposure to O2-lean CO oxidation conditions, FTIR spectroscopy indicates the partial de-confinement of the monoatomic metal centers driven by CO at pre-catalysis temperatures, followed by the development of surface carbonate species under steady-state conditions. These findings are supported by DFT calculations, which show the driving force and final structure for the surface metal protrusion to be metal-dependent, but point to an equivalent octahedral-coordinated M 4+ carbonate species as the resting state in all cases. Experimentally, apparent reaction activation energies in the range of 96±19 kJ/mol are determined, with Pt leading to the lowest energy barrier. The results indicate that, for monoatomic sites in SACs, differences in CO oxidation reactivity enforceable via metal selection are of lower magnitude than those evidenced previously through the mechanistic involvement of adjacent redox centers on the oxide carrier, suggesting that tuning of the oxide surface chemistry is as relevant as the selection of the supported metal.

The primary issue faced by MnO2 cathode materials for aqueous Zn-ion batteries (AZIBs) is the occurrence of structural transformations during cycling, resulting in unstable capacity output. Pre-intercalating closely bonded ions...

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Understanding the redox properties of metal oxide based catalysts is a major task in catalysis research. In situ Electron Paramagnetic Resonance (EPR) spectroscopy is capable to monitor the change of metal ion valences and formation of active sites during redox reactions, allowing for the identification of ongoing redox pathways. Here in situ EPR spectroscopy combined with online gas analysis, supported by ex situ X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), temporal analysis of product (TAP), mass spectrometry (MS) studies was utilized to study the redox behavior of CuOCeO2 catalysts under PROX conditions (preferential oxidation of carbon monoxide in hydrogen). Two redox mechanisms are revealed: (i) a synergetic mechanism that involves the redox pair Ce 4+ /Ce 3+ during oxidation of Cu 0 /Cu + species to Cu 2+ , and (ii) a direct mechanism that bypasses the redox pair Ce 4+ /Ce 3+ . In addition, EPR experiments with isotopically enriched 17 O2 established the synergetic mechanism as the major redox reaction pathway. The results emphasize the importance of the interactions between Cu and Ce atoms for catalyst performance. Guided by these results an optimized CuO-CeO2 catalyst could be designed. A rather wide temperature operation window of 11 degrees (from 377 K to 388 K), with 99% conversion efficiency and 99% selectivity was achieved for the preferential oxidation of CO in a H2 feed.

In this study we show that using AuPd nanoparticles supported on a commercial titanium silicate (TS-1) prepared using a wet co-impregnation method it is possible to produce hydrogen peroxide from molecular H 2 and O 2 via the direct synthesis reaction. The effect of Au: Pd ratio and calcination temperature is evaluated as well as the role of Pt addition to the AuPd supported catalysts. The effect of Pt addition to AuPt nanoparticles is observed to result in a significant improvement in catalytic activity and selectivity to hydrogen peroxide with detailed characterisation indicating this is a result of selectively tuning the ratio of Pd oxidation states.