ABSTRACT
Developing highly efficient and long-durable nanoalloy electrocatalysts toward the hydrogen evolution reaction (HER) are highly desirable for implementation of the water-splitting technique to prepare clean fuels. Though great progress has been achieved, controllable synthesis of hollow NixRuy nanoalloys with a wide component ratio range remains a challenge and their applications for HER have not been explored. Here, a series of necklace-like hollow NixRuy nanoalloys (Ni72Ru28, Ni63Ru37, Ni43Ru57, and Ni29Ru71) are prepared using the galvanic replacement reaction between the Ni nanochains and RuCl3·3H2O and the hollowing process based on the Kirkendall effect. Electrochemical tests reveal that those NixRuy nanoalloys can efficiently catalyze HER in acidic media. Among them, the Ni43Ru57 nanoalloy exhibits the highest catalytic activity with an overpotential of 41 mV to attain a current density of -10 mA cm-2, outperforming other NixRuy nanoalloys and close to commercial Pt/C. Additionally, its current density will exceed Pt/C catalyst as the overpotential surpasses 102 mV. Moreover, such Ni43Ru57 nanoalloy also shows an exceptional durability that can continuously work for 8 h only with a little loss of activity. Deduced from some featured spectroscopic and electrochemical analysis, the excellent catalytic performance of Ni43Ru57 nanoalloy is attributed to the proper component ratio and effective electronic coupling of Ni and Ru, causing the faster interfacial electron transfer kinetics and more available active sites on it compared with other NixRuy nanoalloy ones.
ABSTRACT
3D porous nanoarchitectures derived from SnS/S-doped graphene hybrid nanosheets are successfully prepared by controllable thermal conversion of oleylamine-capped mixed-phase SnS2 -SnS nanodisks precursors, and employed as electroactive material to fabricate flexible, symmetric, all-solid-state supercapacitors. The fabricated solid devices exhibit very high areal specific capacitance (2.98 mF cm-2 ), good cycling stability (99% for 10 000 cycles), excellent flexibility, and desirable mechanical stability.
ABSTRACT
Core-shell nanohybrids containing cheap inorganic nanocrystals and nanocarbon shells are promising electrocatalysts for water splitting or other renewable energy options. Despite that great progress has been achieved, biomimetic synthesis of metal phosphates@nanocarbon core-shell nanohybrids remains a challenge, and their use for electrocatalytic oxygen evolution reaction (OER) has not been explored. In this paper, novel nanohybrids composed of coralloid Co2P2O7 nanocrystal cores and thin porous nanocarbon shells are synthesized by combination of the structural merits of supramolecular polymer gels and a controllable thermal conversion technique, i.e., temperature programmable annealing of presynthesized supramolecular polymer gels that contain cobalt salt and phytic acid under a proper gas atmosphere. Electrocatalytic tests in alkaline solution show that such nanohybrids exhibit greatly enhanced electrocatalytic OER performance compared with that of Co2P2O7 nanostructure. At a current density of 10 mA cm(-2), their overpotential is 0.397 V, which is much lower than that of Co2P2O7 nanostructures, amorphous Co-Pi nanomaterials, Co(PO3)2 nanosheets, Pt/C, and some reported OER catalysts, and close to that of commercial IrO2. Most importantly, both of their current density at the overpotential over 0.40 V and durability are superior to those of IrO2 catalyst. As revealed by a series of spectroscopic and electrochemical analyses, their enhanced electrocatalytic performance results from the presence of thin porous nanocarbon shells, which not only improve interfacial electron penetration or transfer dynamics but also vary the coordination environment and increase the number of active 5-coordinated Co(2+) sites in Co2P2O7 cores.
