Optimizing metal-support interphase for efficient fuel cell oxygen reduction reaction catalyst.

The development of cost-effective and highly-efficient electro-catalysts is essential for the advancement of proton exchange membrane fuel cells (PEMFC). We present a novel nitrogen-sulphur co-doped carbon nanotubes-few layer graphene1D-2D hybrid support formed by partially exfoliating multiwall carbon nanotubes (PECNT), to improve interface bonding to catalyst nanoparticles. Detailed Raman spectroscopy and STEM-EDS analyses demonstrate that active sites on the co-doped hybrid support ensure both uniform distribution and improved bonding of the catalyst nanoparticles to the support. Electrochemical studies show that Pt nanoparticles decorated on nitrogen-sulphur co-doped PECNT (Pt/NS-PECNT) have higher electrochemical active surface area and mass activity accompanied by low H2O2 formation and improved positive half-wave potential, as compared to those decorated on co-doped rGO-incorporated PECNT hybrid structure (Pt/NS-(rGO-PECNT)). Fuel cell measurements demonstrate a higher power density for our novel (Pt/NS-PECNT) electro-catalyst when compared to both Pt/NS-(rGO + PECNT), and commercial Pt/C electro-catalyst. We demonstrate in this work that the interconnectivity between Pt-nanoparticles and the dopant or defect sites on the support play a crucial role in enhancing the ORR activity, fuel cell performance, and durability of the catalyst.

Synergistic Role of Electrolyte and Binder for Enhanced Electrochemical Storage for Sodium-Ion Battery.

Sodium-ion batteries are promising futuristic large-scale energy-storage devices because of the abundance and low cost of sodium. However, the development and commercialization of the sodium-ion battery solely depends on the use of high-capacity electrode materials. Among the various metal oxides, SnO2 has a high theoretical specific capacity for sodium-ion battery. However, the enormous volume expansion and low electrical conductivity of SnO2 hinder its capability to reach the predicted theoretical value. Although different nanostructured designs of electrode materials like SnO2 nanocomposites have been studied, the effects of other cell components like electrolyte and binder on the specific capacity and cyclic stability are yet to be understood. In the present study, we have investigated the synergistic effect of electrolyte and binder on the performance enhancement of SnO2 supported on the intertwined network structure of reduced graphene oxide partially open multiwalled carbon nanotube hybrid as anode in sodium-ion battery. Our result shows that sodium carboxyl methyl cellulose and ethylene carbonate/diethyl carbonate as the electrolyte solvent offers a high specific capacity of 688 mAh g-1 and a satisfactory cyclic stability for 500 cycles. This is about 56% enhancement in specific capacity compared to the use of poly(vinylidene fluoride) binder and propylene carbonate as the electrolyte solvent. The present study provides a better understanding of the synergistic role of electrolyte and binder for the development of metal-oxide-based electrode materials for the advancement of the commercialization of sodium-ion battery.

Application of Few-Layered Reduced Graphene Oxide Nanofluid as a Working Fluid for Direct Absorption Solar Collectors.

Direct absorption solar collectors (DASC) convert solar energy into heat energy and transfer this heat energy to a carrier fluid. Numerical and experimental studies have shown that replacing the absorber medium with nanofluids in DASC increases the efficiency of solar collector significantly. Present work investigates the dispersion stability, optical and thermal properties of reduced few-layered graphene oxide (rGO) dispersed nanofluids for DASC. The synthesis of rGO was carried out by hydrogen exfoliation of graphene oxide at 200 °C. As-synthesized rGO was suitably functionalized to impart the hydrophilic nature. Different characterization techniques were employed to analyze the surface morphology of the sample. Nanofluids were prepared by dispersing calculated amount of functionalized rGO in DI water and ethylene glycol. Optical properties study reveals that the nanofluids exhibit good absorption ability over base fluids. The extinction coefficient of nanofluids showed significant improvement even at low concentration. Furthermore, the temperature dependent thermal conductivity study with different volume fractions, carried out for DI water and ethylene glycol-based nanofluids, shows considerable enhancement.