Dongdong Xu

Coralloid Co2P2O7 Nanocrystals Encapsulated by Thin Carbon Shells for Enhanced Electrochemical Water Oxidation

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.

3D Porous Nanoarchitectures Derived from SnS/S-Doped Graphene Hybrid Nanosheets for Flexible All-Solid-State Supercapacitors.

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.

Component-Controlled Synthesis of Necklace-Like Hollow NiXRuy Nanoalloys as Electrocatalysts for Hydrogen Evolution Reaction

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.

Ru Modulation Effects in the Synthesis of Unique Rod-like Ni@Ni2P–Ru Heterostructures and Their Remarkable Electrocatalytic Hydrogen Evolution Performance

The construction of highly efficient and stable Pt-free catalysts for electrochemical hydrogen generation is highly desirable. Herein, we demonstrate the first metal-phosphides-metal system consisting of Ru, Ni2P, and Ni, which forms unique multiheterogeneous Ni@Ni2P-Ru nanorods. Interestingly, a Ru modulation effects that promotes the desorption of H2 to achieve a moderate hydrogen adsorption energy (ΔGH), and enables the formation of Ni@Ni2P nanorods via Ru-Ni coordination to enhance the conductivity was discovered. Due to its optimal ΔGH, improved conductivity and rod-like morphology, this catalyst shows superior electrocatalytic HER performances in both acidic and alkaline conditions, which are superior to those of some recently reported phosphides and close to that of commercial 20% Pt/C. Such a design strategy is not limited to Ni2P and Ru but also may be extended to other similar phosphides and noble metals, providing a new promising approach and an alternative to Pt catalysts for electrocatalytic applications.

Facile synthesis of ultrathin single-crystalline palladium nanowires with enhanced electrocatalytic activities

Ultrathin single-crystalline palladium nanowires (PdNWs) were rapidly prepared using a facile one-step soft-template-directed method. The utilization of dioctadecyldimethylammonium chloride and an appropriate crystallization temperature determined the construction of PdNWs together. The obtained PdNWs exhibited good electrocatalytic performance toward formic acid oxidation.

Ultrasmall Ru Nanoclusters on Nitrogen-Enriched Hierarchically Porous Carbon Support as Remarkably Active Catalysts for Hydrolysis of Ammonia Borane

The development of the highly active nanocatalysts for effective hydrogen (H2) production is of great significance for its practical applications in fuel cells. Herein, we reported a facile and scale‐up synthetic methodology to grow in situ the remarkably active nanocatalysts of ultrasmall Ru nanoclusters on nitrogen (N)‐enriched hierarchically macroporous‐mesoporous carbon supports (Ru@hPCN). The resultant Ru@hPCN combines structural and chemical merits of well‐dispersed 0.7‐nm Ru nanoclusters, N‐enriched functional surface and 3D hierarchically porous framework, all of which synergistically boost the catalytic performance toward the hydrolysis of ammonia‐borane (AB). An unprecedented activity with a turnover frequency of 1850 min−1 was achieved for the Ru@hPCN, which was 6.0 folds over that of commercialized Ru/C catalyst. Mechanism studies showed that the remarkably enhanced activity can be ascribed to the easier dissociation of electropositive Hδ+ from H2O and the breakage of the B−N bonds as well as favorable mass transport in the Ru@hPCN during AB hydrolysis.

Multimetallic Hollow Mesoporous Nanospheres with Synergistically Structural and Compositional Effects for Highly Efficient Ethanol Electrooxidation

Controlling the nanostructures and chemical compositions of the electrochemical nanocatalysts has been recognized as two prominent means to kinetically promote the electrocatalytic performance. Herein, we report a general “dual”-template synthesis methodology for the formation of multimetallic hollow mesoporous nanospheres (HMSs) with an adjustable interior hollow cavity and cylindrically opened mesoporous shell as a highly efficient electrocatalyst for ethanol oxidation reaction. Three-dimensional trimetallic PdAgCu HMSs were synthesized via in situ coreduction of Pd, Ag, and Cu precursors on “dual”-template structural directing surfactant of dioctadecyldimethylammonium chloride in optimal synthesis conditions. Due to synergistic advantages on hollow mesoporous nanostructures and multimetallic compositions, the resultant PdAgCu HMSs exhibited significantly enhanced electrocatalytic performance toward ethanol oxidation reaction with a mass activity of 5.13 A mgPd–1 at a scan rate of 50 mV s–1 and operation stability (retained 1.09 A mgpd–1 after the electrocatalysis). The “dual”-template route will open a new avenue to rationally design multimetallic HMSs with controlled functions for broad applications.