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Water electrolysis is the most clean and high-efficiency technology for production of hydrogen, an ultimate clean energy in future. Highly efficient non-noble electrocatalysts for hydrogen evolution reaction (HER) are desirable for large scale production of hydrogen by water electrolysis. Especially, exposing as many active sites as possible is a vital way to improve activities of the catalysts. Herein, a series of new hydrangea like composite catalysts of ultrathin Mo 2 S 3 nanosheets assembled uprightly and interlacedly on N, S-dual-doped graphitic biocarbon spheres were facilely prepared. The unique structure endowed the catalysts highly exposed edge active sites and prominently high activities for HER. Especially, the optimized catalyst Mo 2 S 3 /NSCS-50 exhibited as low as 106 mV of overpotential at 10 mA/cm2 (denoted as ƞ 10). The catalyst also showed low Tafel slope of 53 mV/dec, low electron transfer resistance of 34 Ω and high stability evidenced by the result that the current density only attenuated 11.7% after 10 h i-t test. The catalyst has shown broad prospect for commercial application in water electrolysis. • New Mo 2 S 3 ultrathin nanosheets based catalysts have been fabricated for HER. • Mo 2 S 3 ultrathin nanosheets assembled uprightly and interlacedly on carbon spheres. • Hydrangea like composite catalysts were formed based on the above assembly. • The unique structure can provide plenty of exposed edge active sites. • The catalysts exhibited prominent activities and high stabilities for HER. [ABSTRACT FROM AUTHOR]

Development of effective non-noble electrocatalysts for hydrogen evolution reaction (HER) is crucial for hydrogen production by water electrolysis. Herein, several composite catalysts of non-stoichiometric Mo 6 S 9.5 films grown on graphene-like N-doped carbon films were prepared and evaluated for HER in 0.5 M H 2 SO 4. The unique structure endowed the catalysts with highly exposed edge active sites, high specific surface area and prominently high activities for HER. The optimized catalyst exhibited a low overpotential of 113 mV at 10 mA/cm2, a low Tafel slope of 64 mV/dec, and a low charge transfer resistance of 40 Ω along with a highly catalytic stability. [Display omitted] • New Mo 6 S 9.5 ultrathin films based catalysts have been fabricated for HER. • Mo 6 S 9.5 ultrathin films were grown on graphene-like N-doped carbon films. • The unique structure can provide plenty of exposed edge active sites. • The carbon films can improve the conductivity of the catalysts. • The catalysts exhibited prominent activities and high stabilities for HER. [ABSTRACT FROM AUTHOR]

Highly efficient multifunctional earth-abundant elements based electrocatalysts are key important for development of clean energy transformation technologies, such as metal-air batteries, fuel cells and water electrolysis. Herein, composite catalysts of N-doped carbon wrapping Co x P hollow spheres have been successfully prepared by pyrolysis of precursors from self-assembly of cobalt salt, terephthalic acid and PVP followed by carbonization and phosphatization in the presence of sodium hypophosphite. The resulted composites showed high specific surface areas, pore volumes and nitrogen contents, especially more than 47% of pyridinic-N. The electrocatalytic activity tests showed that the optimized Co x P-NC-420 sample exhibited superior multifunctional performances and high stabilities for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) under alkaline conditions. A low overpotential of 125/273 mV (at 10 mA cm−2) and Tafel slope of 66/81 mV dec−1 was obtained for HER and OER, respectively. As for ORR, as high as 0.860 V of half-wave potential was obtained, which is even 36 mV higher than that of Pt/C (20%). The catalyst also exhibited high practical performances on water electrolysis and Zn−air battery. Only 1.61 V of cell voltage was needed to reach 10 mA cm−2 for water electrolysis, and 1.374 V of open-circuit potential and 52 mW cm−2 of power density were obtained for Zn−air battery, which was 16 mW cm−2 higher than that of Pt/C (20%). Moreover, a highly effcient self-driven water electrolyzer has been designed with Co x P-NC-420 as both anode and cathode catalyst, powered by two-series-connected Co x P-NC-420-based Zn–air batteries. This work provides a new strategy for fabrication of non-precious multifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]