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The rate capability of Li-ion batteries is crucially influenced by Li-ion diffusion within bulk electrodes and electrolyte, and Li-ion transfer across the electrode-electrolyte interface. Relative magnitudes of both bulk and interfacial diffusion energy barriers are essential in order to identify the rate-limiting component in overall Li-ion transport process. Here, we quantitatively estimate migration energy barrier in bulk cathode and at the cathode-electrolyte interface through density functional theory based nudged elastic band calculations. We study a Li-ion transfer pathway wherein a Li-ion solvated by the first coordination shell of the electrolyte changes its coordination structure to that in cathode sub-surface sites, and electrolyte molecules act as ligands for Li-ion. We compute the energy barrier for Li-ion transfer from ethylene carbonate/LiPF6 electrolyte into (010)-surface of LiFePO4 to be 756meV. We explore the effect of partial fluorination of interface due to electrolytic reactions and find a drastic reduction in energy barrier to 410meV. Nevertheless, the energy barrier for interfacial ion-transfer is much higher than that for diffusion through bulk one-dimensional channels of olivine LiFePO4, which is estimated at 290meV. The higher energy barrier for interfacial Li-ion transfer suggests a rate-limiting behavior of interface in overall kinetics of ion transport in Li-ion batteries.

An electrochemical approach towards synthesis of highly active, stable and surface selective towards chlorine evolution reaction (CER) of (Zn, Ru)-doped TiO2 (Ru0.26Ti0.73Zn0.01Ox) for the purpose of electrochemical generation of KClO3 is demonstrated. The essential ingredients of this approach consists of (1) co-electrodeposition of Ru, Ti and Zn as metallic alloy and subsequent annealing to oxide (2) dissolution under electrochemically oxidative acidic environment of Ru and Zn-rich surface clusters having high selectivity towards oxygen evolution reaction (OER) leaving Ti-enriched structure that is more selective to CER and (3) using this electrocatalyst for KClO3 production under near-neutral pH conditions. Dissolution of Ru- and Zn enriched surfaces result in higher porosity and surface roughness. Furthermore, this electrochemical dissolution of (Zn, Ru)-rich surface results in electrocatalytic structure that is self-selective towards KClO3 formation with higher specific activity.

Electrochemical chlorine evolution reaction (CER) is one of the most important electrochemical reactions due to importance of Cl2 as an industrial chemical. However, electrochemical CER is bridled with parallel oxygen evolution reaction (OER) reducing the performance of anodic CER In this context, guiding principles behind enhancing the selectivity of CER is investigated experimentally and computationally in RuO2 doped with earth-abundant first-row-transition-metals (i.e. Ti, Fe, Mn, Co, Ni, Cu, Zn). Computational studies suggest that doping of metals having higher d-electrons than Ru in RuO2 tend to lower the binding strength of OER intermediates thereby increasing its overpotential. However, doping has less effect on the binding strength of monovalent CER intermediates resulting in higher CER selectivity. Computational studies suggest that Cu (d9)-doped RuO2 would show maximum CER selectivity and this is corroborated by experiments in acidic medium with electrodeposited Cu-doped RuO2 where 95% selectivity was obtained at a dopant concentration of 2%.

During seawater electrolysis, both oxygen and chlorine evolve at anode and their selectivity can be modulated through variation of surface and electronic structure of the electrocatalyst. In this context, the selectivity toward chlorine evolution reaction (CER) during seawater electrolysis using electrodeposited Cu-doped RuO2 with lower doping concentration (2%) has been found to better than RuO2. Though Cu does not behave as an active site it reduces the binding energy of oxygen evolution reaction (OER) related intermediates (e.g. HO-, O-, HOO-) in neighboring Ru active sites and promotes both specific activity and selectivity of CER as suggested by both experimental and Density Functional Theory studies. However, due to aliovalent nature of Cu-dopant in RuO2 host, phase segregation and surface enrichment of dopants occur with increase in dopant concentration which reduces the overall activity and selectivity toward CER. Furthermore, increase in Cu-dopant would lower surface oxygen vacancy formation energy and promotes additional lattice-oxygen-vacancy aided water dissociation pathway resulting in enhancement of selectivity of OER. The present work offers insight on catalyst design taking account of selectivity of chlorine and oxygen evolution during seawater electrolysis.

We modulate electron-hole separation at semiconductor junctions by stabilization of 'non-native' structures which are nanostructures whose discrete translational symmetry is different from that of the crystalline ground state. Four materials synthesis strategies involving click and colloidal chemistry are discussed and these methods can be potentially generalized to design a range of isomaterial and heteromaterial heterojunctions. The dynamics of electron-hole separation is demonstrated using density functional theory (DFT) which can be experimentally studied also using electrochemical impedance and photolumiscence spectroscopy.

•For the first time, the detailed pilot studies on the weldability, metallurgical and mechanical characterization on EB welded super-duplex stainless steel plates.•Contemplative explanations on the metallurgical and mechanical properties of the weldments.•Balanced austenite–ferrite ratio, superior tensile properties at room temperature.

Approximately 11 million people live in the Terai Alluvial Plain (TAP) of Nepal and about 90% of them entirely depend on groundwater. Recently, the evidence of arsenic contamination in the groundwater of the TAP has been recognized as a public health problem. Till now, about 449,283 tube wells were tested, and 10% of them were found to contain arsenic concentration >10 ppb and 2.6% have >50 ppb. This paper focuses on the sedimentary analysis of aquifer sediments and their source rocks. The study shows the Siwaliks rocks are the possible source of arsenic contamination of groundwater in the TAP.

High energy-density batteries are crucial to energy storage solutions. In lithium-on batteries (LIBs), Si nanopillars are promising anodes due to their highest theoretical specific capacity. However, volume expansion and fracture during cycling inhibit its widespread adaptation. Ge, which is isomorphic with Si, shows better fracture resistance and higher cycle life but has higher molecular weight and cost. Alloying Si with Ge offers a trade-off in optimizing stresses, weight and cost. Here, we computationally evaluate the effect of alloying Si with Ge in reducing stresses generated during lithiation. Hollowing, which creates additional free surface for expansion is also considered. First, we model the stress evolution in nanopillars of Si, Ge, Si-Ge core-shell and Si0.5Ge0.5 alloy. Alloying Si with Ge uniformly, reduces the maximum circumferential stress by around 17%, however, the Si core-Ge shell structure shows stress reduction only when lithiation is confined only to the Ge. Stresses in Si/Ge alloyed nanotubes considering lithiation from the outer boundary as well as from both boundaries are considered. We find a non-monotonous change in lithiation stress with varying radius ratio (R in/R out) and R in/R out = 0.4 leads to the least maximum Hoop stress. The stress reduction in Si-nanotubes in such configuration is found to be 16%.