TiO 2 has been largely explored extensively among other light active metal oxide 112 semiconductors. However, the poor electrical conductivity of TiO 2 is one of the major 113 constraints for its use in commercialization PEC water splitting cells. [26][27][28][29] Other metal oxide 114 6 semiconductors such as ZnO, WO 3 and Fe 2 O 3 have also been widely studied as photoanodes for 115 PEC cells due to their low cost and easy availability for large scale production. [7,[30][31][32][33][34] 116 Among these myriad semiconductors, ZnO is considered as a very promising material for 117 hydrogen generation from PEC water splitting due to its higher electron mobility than TiO 2 118 (155 cm 2 V -1 s -1 for ZnO vs 10 -1 cm 2 V -1 s -1 for TiO 2 ). [35][36][37][38][39][40] However, the wide band gap 119 (3.2 eV) and poor stability of ZnO in the aqueous electrolyte solution result in poor absorption 120 of light and thus, poor photoelectrochemical activity for PEC water splitting.[41] This problem 121 has been recently addressed mainly by tailoring the ZnO electronic structure transforming the 122 band gap to smaller values by doping the structure with metal/non-metal dopant.[41-45] Such a 123 doping strategy is expected to improve photoelectrochemical performance due to improved light 124 absorption occurring as a result of a decrease in the band gap and increase in number of carriers. 125 However, the selection of suitable dopants and their concentration is important for tailoring the 126 band structure of ZnO. Though high concentrations of dopant can offer improved light 127 absorption due to decrease in the band gap, the additional defect levels contributed by dopants in 128 the electronic structure of ZnO can act as recombination sites for photogenerated electron-hole 129 pairs, which results in poor PEC performance and thus, low solar to hydrogen efficiency (SHE), 130 in comparison to undoped ZnO.[46] There has been pioneering research of late conducted into 131 the identification of suitable dopants (such as Cu, N, H, Al, C) for ZnO to achieve superior 132 photoelectrochemical activity for PEC water splitting. The maximum SHE achieved for ZnO 133 based semiconductor material is however only 0.75% for carbon-doped ZnO porous 134 nanoarchitectures.[47] In the aim of attempting to commercialize PEC water splitting for 135 economic production of hydrogen, it is important to improve SHE beyond 0.75%.[48, 49] This136 157 (x=0.05), based on the results of photoelectrochemical characterization discussed later, is further 158 improved by N-doping in (Zn 1-x Co x )O NWs (x=0.05). The study of nitrogen doped TiO 2 by 159 8 Hoang et al. has demonstrated that nitrogen is a potential anionic dopant for TiO 2 [59], wherein 160 N-doping in TiO 2 offered improved carrier density, reduced band gap with improved light 161 absorption in the visible region of interest, improved charge separation, transport and collection 162 and improved SHE, compared to pure TiO 2 . The improved photo-response after N doping in 163 TiO 2 can be at...

Nanocrystalline vanadium nitride (VN) has been synthesized using a simple two-step procedure involving mechano-chemical reaction of V2O3 and Li3N mixture induced by high energy mechanical milling (HEMM) followed by washing in water. The crystalline VN thus synthesized has been analyzed as a supercapacitor material in aqueous media. The electrochemical mechanism and material properties influencing the supercapacitor behavior of VN have been explored. The surface properties of the nanocrystalline VN have also been studied using X-ray photo-electron spectroscopy (XPS) and correlated to the electrochemical response. Stable capacitances of upto 60 F/g are reported here for nanocrystalline VN generated using the high energy mechano-chemical reaction method. Cycling induced degradation of capacitance has also been studied and the possible degradation mechanisms have been discussed.

Lithium-sulfur (Li-S) secondary batteries with sulfur cathodes and theoretical energy density of ∼2600 Wh/kg, are promising high energy-density system for next-generation electric-vehicles (EVs) potentially mitigating the gravimetric and volumetric energy density limitations of existing lithium-ion (Li-ion) batteries. Herein, a chemically synthesized sulfonic acid-based complex framework material (CFM) termed as (SCFM), was used as sulfur host (S-SCFM) to prevent polysulfide dissolution in Li-S batteries. The S-SCFM based CFM cathodes show an initial capacity of 1190 mAh/g and a capacity of 1044 mAh/g after 100 cycles. In addition, the S-SCFM based CFM cathodes exhibited good cycling stability with a minimal fade rate of ∼0.0012% per cycle. XPS analysis of the cycled separators with the S-SCFM electrodes shows complete absence of polysulfide species after 100 charge-discharge cycles. It was also identified that the SCFM based CFM chemically binds sulfur via -C-S-linkages thereby exhibiting an affinity for the polysulfide species formed during the charge-discharge cycles. As a result, the SCFM based CFM prevent polysulfide species from dissolving and diffusing into the electrolyte. A thorough understanding of these engineered SCFM based CFM sulfur host in Li-S battery outlined herein will be vital in designing promising sulfur hosts for next generation sulfur cathodes in Li-S batteries.

A simple, facile, and more importantly, recyclable sacrificial template based approach involving magnesium oxide (MgO) nanorods for producing scalable quantities of hollow silicon nanotubes (h-SiNTs) architectures is discussed in this report.