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Energy storage and conversion driven by electro-or photocatalyst is a highly exciting field of research, and generations of effective and durable oxide catalysts have received much attention in this field. Here, we report A-site lanthanum-doped oxygen-rich quinary oxide CaLaScRuO 6+δ synthesized by adopting the solid-state reaction method and characterized by various techniques such as powder X-ray diffraction, neutron diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma-atomic emission spectrometry, Raman spectroscopy, and temperature-programmed reduction in the presence of a hydrogen atmosphere (H 2 -TPR). X-ray absorption study confirms the existence of mixed valent Ru ions in the structure, which enhances the oxygen stoichiometry for the partial balance of an extra cationic charge. Neutron powder diffraction and reduction of the material in a hydrogen atmosphere (H 2 -TPR) can confirm the oxygen overstoichiometry of the catalyst. The present material works as an efficient and robust oxygen bifunctional electrocatalyst for ORR/ OER (oxygen evolution reaction/oxygen reduction reaction) followed by four-electron transfer pathway in a strong (1 M KOH) alkaline medium. The catalytic nature of the designed structural and chemical flexible perovskite is a novel example of an electrocatalyst for the oxygen bifunctional activity.

An Energy Scanning X-ray Absorption Fine Structure spectroscopy beamline has recently been installed and commissioned at BL-09 bending magnet port of INDUS-2 synchrotron source, Indore. The beamline uses an UHV compatible fixed exit double crystal monochromator (DCM) with two Si (111) crystals. Two grazing incidence cylindrical mirrors are also used in this beamline; the pre-mirror is used as a collimating mirror while the post mirror is used for vertical focusing and higher harmonic rejection. In this beamline it is possible to carry out EXAFS measurements both in transmission and fluorescence mode on various types of samples, using Ionization chamber detectors and solid state drift detector respectively. In this paper, results from first experiments of the Energy Scanning EXAFS beamline are presented.

Summary Detailed investigations of CuCl2 hydrolysis step of Cu–Cl thermochemical cycle were carried out on various aspects: (a) characterization and thermal properties of reactants/products using X‐ray diffraction (XRD), thermogravimetry–mass spectrometry (TG‐MS), scanning electron microscopy (SEM), temperature‐programmed desorption (TPD), and extended X‐ray absorption fine structure (EXAFS); (b) performance evaluation of fixed bed hydrolysis; (c) parametric optimization with respect to S/Cu, flow rate (gas hourly space velocity, GHSV), reaction duration, temperature, and particle size; and (d) monitored hydrolysis using isothermal TG experiments at 360°C, 370°C, 380°C, 390°C, and 400°C to derive kinetic parameters rate constant (k) and activation energy (Ea) on the basis of the shrinking‐core model. 97% conversion to Cu2OCl2 at 17 630 h−1 of GHSV, 400°C was achieved using ball‐milled CuCl2 (BM6), as compared with that of 55% over commercial un–ball‐milled reactant, CuCl2 (UBM). Correspondingly, higher k value of 2.84 h−1 over BM6 as compared with 0.97 h−1 over UBM reactant at 400°C was achieved. Ea for hydrolysis of BM6 was 93 kJ/mol, while it was 106 kJ/mol for UBM as derived from the Arrhenius plot. A probable pathway for CuCl2 hydrolysis is proposed here. It was found to be diffusion controlled, and the particle size of reactant molecules affects the packing and diffusion length. Based on our investigations, it is very unlikely to get >99% phase pure product (Cu2OCl2). Cu2OCl2 is labile in nature and tends to transform into structurally similar and stable compounds CuO and CuCl2.

Activator-free zinc aluminate (ZA) nanophosphor was synthesized through a sol-gel combustion route, which can be used both as a blue-emitting phosphor material and a white-emitting phosphor material, depending on the annealing temperature during synthesis. The material also has the potential to be used in optical thermometry. These fascinating color-tunable emission characteristics can be linked with the various defect centers present inside the matrix and their changes upon thermal annealing. Various defect centers, such as anionic vacancy, cationic vacancy, antisite defect, etc., create different electronic states inside the band gap, which are responsible for the multicolor emission. The color components are isolated from the complex emission spectra using time-resolved emission spectroscopy (TRES) study. Interestingly, the lifetime values of the various defect centers were found to change significantly from milliseconds to microseconds upon thermal annealing, which makes the phosphors more diverse (i.e., either long-persistent blue-emitting phosphors or short-persistent white-emitting phosphors). Fourier transform infrared (FTIR) and diffuse reflectance spectroscopy (DRS) confirmed the presence of antisite defect centers such as Al or Zn in the matrix. X-ray absorption fine structure (EXAFS) study showed that the spinel structure was more disordered in nature for low-temperature-annealed compounds. Electron paramagnetic resonance (EPR) and positron annihilation lifetime spectroscopy (PALS) studies were also carried out in order to characterize various anionic and cationic vacancies and their clusters present in the compounds. Antisite defect centers such as Al or Zn, which act as an electron or hole trap, were found to be responsible for the diverse lifetime behavior. To gain insight about the electronic states inside the band gap, density functional theory (DFT)-based calculations were performed for both pure and various vacancy-introduced spinel structures. Finally, based on the theoretical and experimental results, for the first time, a detailed investigation of various defect-induced emission behavior in ZA is presented, which also explains the mechanism of color tunability and dynamic lifetimes.

Rational engineering of atomically scaled metalnitrogen-carbon (M-N-C) moieties has been the topic of recent research interest because of their potential application as an electrochemical oxygen reduction reaction (ORR) catalyst. Despite numerous efforts on M-N-Cs, attaining both adequate activity and a satisfactory stability simultaneously is a principal issue. Herein, we demonstrated the synthesis of a single-atom tungsten catalyst supported on the N-doped carbon matrix (W-N-C) and its application as an ORR catalyst. W-N-C was synthesized using the economically viable, simple, one-step pyrolysis of dicyandiamide and tungsten(VI) chloride at moderate temperature (700 °C). The synthesis of W-N-C avoids any post acid treatment as it does not require any subsidiary sacrificial metal like Zn and, hence, does not induce any burden associated with chemical waste management. The atomic dispersion of W atoms stabilized by N-doped porous carbon and the formation of WN 2 C 2 were confirmed by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption spectroscopy. Interestingly, as-synthesized WN 2 C 2 exhibited unprecedented electrocatalytic activity with a half-wave potential of 764 mV vs reversible hydrogen electrode (RHE) as well as significantly enhanced stability (retaining >99% diffusion-limited current density and the loss in activity is 10.5% at 0.84 V after 10,000 potential cycles), which is much better than the stability limit set by the US Department of Energy in an alkaline medium. Overall, the activity of W-N-C surpasses that of Pt/C after 5000 cycles. The excellent stability is believed to be due to the symmetric coordination of the metal active site (W 2 N 2 C 2 ).

Compression-induced (≤1.01 GPa) phase transformation, local deformations, and pore architecture modifications in zeolitic-imidazole framework (ZIF-8) powder have been investigated, ex situ, using X-ray diffraction, extended X-ray absorption fine structure, Fourier transform infrared, and positron annihilation lifetime spectroscopy. Compression-induced reduction in crystallinity leading to partial amorphization of ZIF-8 is observed to be an irreversible phenomenon. The amorphization of ZIF-8 was accompanied by local deformations in imidazolate ring bonding. The study has confirmed the retention of Zn–N tetrahedral arrangement in the amorphous state of the framework through X-ray absorption measurements. The phase transformation and local deformations lead to modifications in powder morphology as well as reduction in internal porosity of the framework. The triplet state of positronium (o-Ps) has been used to investigate the pressure-induced pore architecture modifications. At the lowest applied pressure (0.20 GPa), partial collapse of open free volume inside the crystalline ZIF-8 leading to reduction in internal porosity has been observed, while the crystal structure is maintained. On further increasing the pressure, amorphization of ZIF-8 is observed leading to cataclysmic modifications in the pore architecture. The amorphous phase of the framework possesses a continuous random network of open volumes having a broader size distribution with fewer interconnections as compared to the crystalline counterpart. The present study also indicates the evolution of a new crystalline topology of ZIF-8 at applied pressure of 1.01 GPa through complementary techniques.