Yanhui Wang

A Ti-coated nano-SiC supported platinum electrocatalyst for improved activity and durability in direct methanol fuel cells

Nano-silicon carbide (nano-SiC) particles modified with a titanium (Ti) coating were used as a novel support for the platinum (Pt) electrocatalyst in direct methanol fuel cells. Ti-coated nano-SiC (Ti/SiC) powder was prepared by a one-pot deposition method under vacuum and a coating was formed on the nano-SiC surface. The Ti coating was strongly bonded with nano-SiC with the help of TiC and Ti5Si3. The Ti/SiC supported Pt electrocatalyst (Pt–Ti/SiC) was fabricated using a microwave-assisted reduction method. The electrocatalytic performances of the Pt–Ti/SiC for the methanol oxidation and oxygen reduction reactions were much higher than the Pt supported on the pristine nano-SiC. The electrochemical stability of the Pt–Ti/SiC was more outstanding compared with the Pt supported on Vulcan XC-72 carbon black. The superior electrocatalytic performance of the Pt–Ti/SiC can be ascribed to the anchoring effect of the Ti coating on Pt nanoparticles and the high stability of the nano-SiC support.

A microwave-assisted synthesis of CoO@Co core–shell structures coupled with N-doped reduced graphene oxide used as a superior multi-functional electrocatalyst for hydrogen evolution, oxygen reduction and oxygen evolution reactions

A novel electrochemical catalyst comprising CoO@Co nanoparticles with a core–shell structure immobilized on N-doped reduced graphene oxide (rGO) (CoO@Co/N-rGO) has been synthesized using a convenient and controllable technique — combining a rapid microwave-polyol method with a vacuum thermal treatment. Excellent features including the Co/N-doping effect, introduction of CoO@Co particles with a core–shell structure and good contact between the CoO@Co particles and N-doped graphene result in a highly multi-functional catalytic efficiency. The catalyst exhibits remarkable catalytic activity and superior stability towards the hydrogen evolution reaction, offering a low overpotential of 140 mV for 10 mA cm−2 in 0.5 M H2SO4 and 237 mV in 0.1 M KOH. The catalyst also shows excellent oxygen reduction reaction activity in 0.1 M KOH, a similar four-electron pathway, which is comparable to that of a commercial Pt/C catalyst, and superior stability. In addition, a good electrochemical performance towards the oxygen evolution reaction was observed for the catalyst, achieving a current density of 10 mA cm−2 with a small overpotential of 1.67 V in 0.1 M KOH, which is comparable to that of a commercial RuO2 catalyst. The unusual catalytic activities arise from the synergetic chemical coupling effects of metallic Co, cobalt oxides and Co/N-doped graphene. This study provides a new attractive multi-functional catalyst material for unitized regenerative fuel cells and overall water splitting technologies.

Inhibiting the oxidation of diamond during preparing the vitrified dental grinding tools by depositing a ZnO coating using direct urea precipitation method.

Oxidation of diamond during the manufacturing of vitrified dental grinding tools would reduce the strength and sharpness of tools. Zinc oxide (ZnO) coating was deposited on diamond particles by urea precipitation method to protect diamond in borosilicate glass. The FESEM results showed that the ZnO coating was formed by plate-shaped particles. According to the TG results, the onset oxidation temperature of the ZnO-coated diamond was about 70 °C higher than the pristine diamond. The EDS results showed that ZnO diffused into the borosilicate glass during sintering. As the result, the bending strength of the composites containing ZnO-coated diamond was increased by 24% compared to that of the composites containing pristine diamond.

Si3N4 whiskers modified with titanium as stable Pt electrocatalyst supports for methanol oxidation and oxygen reduction

Ti-modified Si3N4 (Ti/Si3N4) whiskers were modified with titanium by a one-pot deposition method in a vacuum. Pt electrocatalysts supported on Ti/Si3N4 (Pt–Ti/Si3N4) were fabricated using a microwave-assisted reduction method. A Ti coating was formed on the surface of Si3N4 and strongly bonded with Si3N4 with the assistance of TiNx and Ti5Si3. In this paper, the Pt–Ti/Si3N4 electrocatalysts demonstrated outstanding electrochemical stability and excellent electrocatalytic activity toward the methanol oxidation and oxygen reduction reactions compared to the Pt supported on pristine Si3N4.

One-pot synthesis of a Mn(MnO)/Mn5C2/carbon nanotube nanocomposite for supercapacitors

We report a one-pot synthesis of Mn(MnO)/Mn5C2/carbon nanotube (CNTs) nanocomposite for supercapacitors. The Mn(MnO)/Mn5C2/CNTs composed of Mn(MnO) nanoflakes bonded with CNTs through interfacial Mn5C2 carbides was prepared by heating a mixture of Mn powder and CNTs at 600 °C under vacuum. The carbides obtained by an in situ reaction provided strong interface bonding between the CNTs and Mn(MnO), and consequently enhanced stability of the nanocomposite as a supercapacitor electrode material. The capacitive properties of the Mn(MnO)/Mn5C2/CNTs electrodes were investigated by a cyclic voltammetry (CV) test in a 0.5 M Na2SO4 aqueous solution. The Mn(MnO)/Mn5C2/CNTs prepared at 600 °C for 1 h displayed a maximum specific capacitance of 378.9 F g−1 (based on total mass of active materials) at 2 mV s−1. The long-term cycling stability of the Mn(MnO)/Mn5C2/CNT electrode was investigated by repeating the CV test from 0.1 and 0.8 V (vs. SCE) at 100 mV s−1. Contrary to a traditional MnO2/CNTs electrode, whose specific capacitance would decrease with cycle number, the Mn(MnO)/Mn5C2/CNTs had an increased specific capacitance at the initial 450 cycles. This phenomenon is because of an electrochemical conversion from Mn(MnO) to MnO2 in the initial CV test. Little decrease in the specific capacitance was found even after 1000 cycles, indicating an excellent cycling stability. These properties are attributed to the unique Mn(MnO)/Mn5C2/CNT structure.

Co2B and Co Nanoparticles Immobilized on the N–B-Doped Carbon Derived from Nano-B4C for Efficient Catalysis of Oxygen Evolution, Hydrogen Evolution, and Oxygen Reduction Reactions

A novel hybrid electrocatalyst of Co2B and Co nanoparticles immobilized on N-B-doped carbon derived from nano-B4C (Co2B/Co/N-B-C/B4C) is in situ synthesized by pyrolysis of nano-B4C supporting Co(OH)2 nanoparticles with melamine. The Co2B and Co nanoparticles are formed and anchored on the generated N and B codoped carbon and undecomposed B4C. The hybrid exhibits remarkable catalytic performances toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR)-a very small potential of 1.53 V at 10 mA cm-2 for the OER and a high catalytic kinetics and superior durability for the ORR-which are superior to the RuO2 and Pt/C catalyst, respectively. Most impressively, the hybrid delivers a very small potential gap of 710 mV, which is lower than those of most bifunctional electrocatalysts reported. In addition, the hybrid also shows a satisfying hydrogen evolution reaction performance offering a small overpotential of 220 mV at 10 mA cm-2 and wonderful stability. The excellent trifunctional catalytic performances issue from synergetic effects of Co2B, metal Co, Co/N-doped carbon, and B self-doped carbon coexisting in the hybrid with good interaction mutually. This work provides a new-type efficient multifunctional catalyst for regenerative fuel cell and overall water-splitting technologies.

A novel hybrid of Ni and WC on new-diamond supported Pt electrocatalyst for methanol oxidation and oxygen reduction reactions

A hybrid of nickel and tungsten carbide on new‐diamond (Ni‐WC/nD) was synthesized by a microwave‐assisted method, in which nickel(tungsten) hydroxide was deposited on carbon black and then reduced carbothermally under N2 atmosphere. Pt nanoparticles (NPs) were deposited on the hybrid to form the Pt/Ni‐WC/nD electrocatalyst. XRD and TEM were used to investigate the structure and morphology of Pt/Ni‐WC/nD, respectively. The results revealed that Ni and WC particles formed on carbon black during the reduction of nickel(tungsten) hydroxide at 1300 °C under N2, and the amorphous carbon was translated to new‐diamond as a result of the catalysis of Ni. The Pt NPs deposited on Ni‐WC/nD exhibited a good affinity with the support. We demonstrated that Pt/Ni‐WC/nD was an active electrocatalyst for the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR). Pt/Ni‐WC/nD exhibited a better electrocatalytic activity and durability than Pt/C electrocatalyst for the MOR and ORR. This can be attributed to the strong interaction between the Ni‐WC/nD support and Pt and the excellent stability of the new‐diamond.