Exploration of high-efficiency Pt-free electrochemical catalysts for hydrogen evolution reaction (HER) is considered as a great challenge for the development of sustainable and carbon dioxide free energy conversion systems. In this work, a unique hierarchical nanostructure of few-layered MoSe2 nanosheets perpendicularly grown on carbon nanotubes (CNTs) is synthesized through a one-step solvothermal reaction. This rationally designed architecture based on a highly conductive CNT substrate possesses fully exposed active edges and open structures for fast ion/electron transfer, thus leading to remarkable HER activity with a low onset potential of -0.07 V vs. RHE (reversible hydrogen electrode), a small Tafel slope of 58 mV per decade and excellent long-cycle stability. Therefore, this noble-metal-free and highly efficient catalyst enables prospective applications for industrial, renewable hydrogen production.

† Footnotes relating to the title and/or authors should appear here. Electronic Supplementary Information (ESI) available: Low magnification SEM images of SnCl2/PVP precursor nanofibers, SnO2 nanotubes and SnO2@MoSe2-3 hybrids, respectively; SEM image of pure MoSe2 nanospheres; EDS spectrum of SnO2@MoSe2-3 hybrid; Nitrogen adsorption/desorption isotherms; Morphology of SnO2@MoSe2-3 composite after 3000 CV cycles. See

h i g h l i g h t sFe-La composite (hydr)oxides were synthesized via coprecipitation method. Fe-La composite (hydr)oxides were effective for arsenate removal from water. As(V) was removed by both precipitation and sorption under acidic condition. As(V) removal was achieved by adsorption under alkaline condition. t r a c tArsenic exists ubiquitously in the environment and has been proved to be of great harm to human health. In this study, a series of Fe-La composite (hydr)oxides were synthesized via a facile coprecipitation for effective As(V) removal from aqueous solution. A variety of techniques including BET surface area measurement, powder XRD, SEM, and XPS were employed to characterize the synthetic Fe-La composite (hydr)oxides. Fe-La composite (hydr)oxides grains were formed via aggregation of primary nanoparticles. With an increase in La content, the specific surface area of Fe-La composite (hydr)oxides decreased, but the pore diameter, the pore volume and the grain size of Fe-La composite (hydr)oxides increased gradually. Rapid As(V) adsorption on the synthesized composite oxides was achieved and the adsorption was well fitted by the pseudo-second-order equation. The adsorption isotherms could be well described by Langmuir equation and the maximal adsorption capacity of Fe-La composite (hydr)oxides can reach 368 mg/g. The As(V) removal was pH-dependent and decreased with an increase in pH value, especially in alkaline condition. Under acidic and neutral conditions, As(V) removal was mainly achieved by both precipitation and adsorption. By contrast, adsorption is the only mechanism for As(V) removal in alkaline condition. The results indicate that the Fe-La composite (hydr)oxides could be potentially attractive adsorbents for As(V) removal.

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