Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

Composites of poly­(vinylidene fluoride-co-hexafluoro propylene) (PVdF-HFP) incorporating 10 wt % bis­(trifluoromethane)­sulfonimide lithium salt (LiTFSI) and 10 wt % particles of nanoparticulate silica (nm-SiO2), nanoparticulate titania (nm-TiO2), and fumed silica (f-SiO2) were prepared by electrospinning. These membranes served as host matrix for the preparation of composite polymer electrolytes (CPEs) following activation with lithium sulfur battery electrolyte comprising 50/50 (vol %) dioxolane/dimethoxyethane with 1 M LiTFSI and 0.1 M LiNO3. The membranes consist of layers of fibers with average fiber diameter of 0.1–0.2 μm. CPEs with f-SiO2 exhibited higher ionic conductivity with a maximum of 1.3 × 10–3 S cm–1 at 25 °C obtained with 10 wt % filler compositions. The optimum CPE based on PVdF-HFP with 10 wt % f-SiO2 exhibited enhanced charge–discharge performance in Li-S cells at room-temperature eliminating polysulfide migration, delivering initial specific capacity of 895 mAh g–1 at 0.1 C-rate and a very low electrolyte/sulfur (E/S) ratios between 3:1 to 4:1 mL.g–1. The CPEs also exhibited very stable cycling behavior well over 100 cycles (fade rate ∼ 0.056%/cycle), demonstrating their suitability for Li-S battery applications. In addition, the interconnected morphological features of PVdF-HFP result in superior mechanical properties (200–350% higher tensile strength). Higher Li-ion conductivity, higher liquid electrolyte uptake (>250%) with dimensional stability, lower interfacial resistance, and higher electrochemical stability are some of the attractive attributes witnessed with these CPEs. With these improved performance characteristics, the PVdF-HFP system is projected herein as suitable polymer electrolytes system for high-performance Li–S rechargeable batteries.

Long term cyclability of a composite Li-ion anode electrode comprised of 82 wt.% Si/C lithium ion active material along with 8 wt.% polymeric binder and 10 wt.% Super P conductive carbon black has been studied utilizing polymeric binders exhibiting different elastic/tensile moduli and tensile yield strengths. Accordingly electrochemically active Si/C composite synthesized by high energy mechanical milling (HEMM), exhibiting reversible specific capacities of ~780mAh/g and ~600mAh/g at charge/discharge rates of ~50mA/g and ~200mA/g, respectively were selected as the Li-ion active anode. Polyvinylidene fluoride (PVDF) and purified guar gum (PGG) with reported elastic modulus ~1000MPa and ~3200MPa, respectively were selected as the binders.Results show that the composite electrode (Si/C + binder + conducting carbon) comprising the higher elastic modulus binder (PGG) exhibits better long term cyclability contrasted with PVDF. 1 H NMR analysis of the polymer before and after cycling shows structural degradation/deformation of the low elastic modulus PVDF, whereas the high elastic modulus PGG binder shows no permanent structural deformation or damage. The results presented thus suggest that PGG based polymers exhibiting high elastic modulus are a promising class of binders with the desired mechanical integrity needed for enduring the colossal volume expansion stresses of Si/C based composite anodes.

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...

human biomechanical energy harvesting a promising clean alternative to electrical power supplied by batteries. [1,2] Human biomechanical energy harvesting generally refers to converting mechanical energy available from various sources in the human body to electrical energy. There are two sources of human biomechanical energy: momentary and spontaneous. Momentary sources include discontinuous activities such as walking, running, upper limb motions, etc., whereas spontaneous sources include continuous activities such as blood pressure, respiration, etc. [3][4][5] Recently, triboelectric nanogenerators (TENGs) that work on a combination of contact electrification and electrostatic induction, have been demonstrated as a promising technology for human biomechanical energy harvesting (walking/ footfalls, [6][7][8][9] upper limb motions, [10][11][12][13] textile-based, [14][15][16][17] etc.). TENGs offer numerous advantages over electromagnetic, piezoelectric, and electrostatic based energy harvesting technologies, namely, low cost, light weight, diverse choice of fabrication materials, and high adaptability design, thus making them more suitable for energy harvesting from low frequency human body motion. [18][19][20] Respiration is a spontaneous source of human biomechanical energy that is currently untapped, and has the potential of being a sustainable power source for low power wearable electronic devices and integrated body sensor networks. Respiratory energy can be harvested and converted to electricity from: (a) flow of air, and (b) abdomen/chest motion. Piezoelectric [21] and electromagnetic [22] energy harvesting techniques have been proposed to harvest energy from air-flow during respiration. However, these would require the user to wear a face mask, which limits real-life applications. In another approach, a TENG is implanted within a rat to convert the mechanical energy from periodic expansion and contraction of the thorax, which is geared toward powering implanted medical devices. [23] For utilizing energy from respiratory motion to power wearable electronics via a TENG, a noninvasive and comfortable approach is desirable. To evaluate this, we conducted a preliminary feasibility study which indicated the potential of using a contact-separation mode based TENG to harvest energy from a low frequency motion. [24] In this paper, a TENG based on contact-separation mode is demonstrated as a The need to recharge and eventually replace batteries is increasingly significant for operating a variety of wearable electronic devices. Rapid advances in low power design have stimulated the requirements for portable and sustainable power sources, thus opening the possibility of using human biomechanical energy as a promising alternative power source. Respiration is a unique form of spontaneous and stable source of human biomechanical energy that is currently untapped, and has the potential to be converted to a sustainable power source for low power wearable electronic devices and integrated body sensor networks. However, eff...