No abstract

Tunable palladium nanonetwork (PdNN) has been developed for catalyzing ethanol oxidation reaction (EOR) and hydrogen evolution reaction (HER) in alkaline electrolyte. 3D PdNN is regarded as a dual active electrocatalyst for both EOR and HER for energy conversion application. The PdNN has been synthesized by the simple chemical route with the assistance of zinc precursor and a surfactant (i.e., cetyltrimethylammonium bromide, CTAB). The thickness of the network can be tuned by simply adjusting the concentration of CTAB. Both EOR and HER have been performed in an alkaline electrolyte, and characterized by different voltammetric methods. The 3D PdNN has shown 2.2-fold higher electrochemical surface area than the commercially available Pt/C including other tested catalysts with minimal Pd loading. As a result, it provides a higher density of EOR and HER active sites and facilitated the electron transport. For example, it shows 2.6-fold higher mass activity with significantly lower CO production for EOR and the similar overpotential (110 mV @ 10 mA cm) for HER compared to Pt/C with better reaction kinetics for both reactions. Thus, the PdNN is proved as an efficient electrocatalyst with better electrocatalytic activity and stability than state-of-the-art Pt/C for both EOR and HER because of the crystalline, monodispersed, and support-free porous nanonetwork.

We have reported the synthesis and application of carbon nanotubes supported δ-MnO2 (δ-MnO2/CNTs) nanocomposite as enzyme-free sensor for the detection of H2O2, where δ-MnO2 serves as the catalytic center and CNTs as the highly conductive base.

the metal-free nitrogen-doped graphitic-carbon@graphene (ng-c@G) is prepared from a composite of polyaniline and graphene by a facile polymerization following by pyrolysis for electrochemical oxygen reduction reaction (oRR). pyrolysis creates a sponge-like with ant-cave-architecture in the polyaniline derived nitrogenous graphitic-carbon on graphene. the nitrogenous carbon is highly graphitized and most of the nitrogen atoms are in graphitic and pyridinic forms with less oxygenated is found when pyrolyzed at 800 °C. The electrocatalytic activity of Ng-C@G-800 is even better than the benchmarked Pt/C catalyst resulting in the higher half-wave potential (8 mV) and limiting current density (0.74 mA cm −2) for oRR in alkaline medium. Higher catalytic performance is originated from the special porous structure at microscale level and the abundant graphitic-and pyridinic-n active sites at the nanoscale level on carbon-graphene matrix which are beneficial to the high O 2-mass transportation to those accessible sites. Also, it possesses a higher cycle stability resulting in the negligible potential shift and slight oxidation of pyridinic-n with better tolerance to the methanol. To save the world from day-by-day increasing energy demands and environmental concerns, the clean, highly efficient and renewable energy technologies are immediately required to be implemented 1. Among various renewable energy technologies, fuel cells (FCs) and metal-air batteries are regarded as the promising clean energy sources because of their high energy conversion efficiency and emission-free power generation 2,3. However, the efficiency of those technologies is strongly depend on the reaction kinetics which are involving with 4. For example, the sluggish kinetics of cathodic oxygen reduction reaction (ORR) hinders the overall performance of FCs 5. Thus, FCs require a highly active and durable electrocatalysts for increasing ORR kinetics. Although, Pt-based materials have been used as the state-of-the-art electrocatalysts for ORR because of their higher current density with lower overpotential compared to other electrocatalysts 6,7 , but their poor durability and prohibitive cost are hampering widespread usage of FCs technology in practical life 6,7. In recent past, researchers are focusing on nitrogen-doped carbon materials (NCMs) with various extrabeneficial features as metal-free ORR catalysts which shown to be an efficient, durable and carbon monoxide (CO)-poisoning-free substitute to Pt-based catalysts 4,8-10. Although, the previous research has shown that the significant improvement has done for ORR catalysis on NCMs, still the ORR performance needs to be improved 11. There are two important approaches are strongly correlated to the improvement of the ORR electrocatalytic activity of NCMs. One is to enhance the intrinsic activity of doped nitrogen and the other one is to increase the number of active sites 4. For enhancing the intrinsic activity of NCMs, they should be engineered to contain a high number of active sites with better exp...