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Designing advanced electrocatalysts for hydrogen evolution reaction is of far-reaching significance. Active sites and conductivity play vital roles in such a process. Herein, we demonstrate a heteronanostructure for hydrogen evolution reaction, which consists of metallic 1T-MoS2 nanopatches grown on the surface of flexible single-walled carbon nanotube (1T-MoS2/SWNT) films. The simulated deformation charge density of the interface shows that 0.924 electron can be transferred from SWNT to 1T-MoS2, which weakens the absorption energy of H atom on electron-doped 1T-MoS2, resulting in superior electrocatalytic performance. The electron doping effect via interface engineering renders this heteronanostructure material outstanding hydrogen evolution reaction (HER) activity with initial overpotential as small as approximately 40 mV, a low Tafel slope of 36 mV/dec, 108 mV for 10 mA/cm2, and excellent stability. We propose that such interface engineering could be widely used to develop new catalysts for energy conversion application. [ABSTRACT FROM AUTHOR]

Ultrathin inorganic nanosheets that enable fast electrochemical reaction kinetics are highly required in many energy-related applications. Herein, we report a simple strategy for in situ assembly of ultrathin NiCo2O4 nanosheets with enriched surface active sites on graphene surface in a vertical orientation way by employing polyaniline (PANI) as the structure coupling bridge between the two components (denoted by NiCo2O4-P-G). The as-made ultrathin NiCo2O4 nanosheets are rich in metal ions in high valence state and oxygen defective sites, and feature 3D open frameworks with hierarchical pore structure. It has been found that the nitrogen species derived from PANI building blocks as bridging sites tend to bond with metal ions, which effectively tune the electronic structural states and result in strong coupling effects with the NiCo2O4 nanosheets. Benefiting from these structural characteristics, the as-made NiCo2O4-P-G hybrids, when used as pseudocapacitive electrode materials, can deliver a high specific capacitance of 966 F g-1 (based on the mass of the active NiCo2O4 component) and an excellent rate capability of ca. 84% even the current density increased by 100 times and long-term stability. As the precious metal-free electrocatalyst for the oxygen evolution (OER) reaction, the NiCo2O4-P-G hybrids are also able to deliver a low overpotential of 0.32 V at a current density of 10 mA cm-2 in 0.1 M KOH aqueous electrolyte (only 70% iR compensation), holding promise for high performance yet cheap electrocatalysts for the OER reaction. [ABSTRACT FROM AUTHOR]

Lithium-oxygen batteries (LOBs) and direct methanol fuel cells (DMFCs) are both attractive technologies for the development of future energy storage and conversion devices, while the lack of highly active electrocatalysts has largely hampered their large-scale commercial applications. In the present work, we have demonstrated the controllable synthesis of nitrogen and sulfur codoped graphene (NS-G) nanosheets via a simple and cost-effective approach. Owing to their distinctive structural advantages, such as large surface areas, good flexibility, coexistence of N and S atoms with tunable doping contents and positions, and high electrical conductivity, the obtained NS-G sheets exhibit low discharge-recharge voltage gaps and high round-trip efficiencies as well as exceptional rate capability when used as cathode materials for LOBs. Furthermore, the NS-G layers are also identified to be an ideal substrate for the decoration of ultrafine Pt nanoparticles. Benefiting from the synergetic effects, exceptional electrocatalytic properties including high activity, strong poison tolerance, and outstanding long-term stability are observed for the resulting Pt/NS-G hybrid toward methanol oxidation reaction, which are significantly superior to those for Pt/undoped graphene and commercial Pt/C catalysts. [ABSTRACT FROM AUTHOR]