A laser synthesis of vanadium oxide bonded graphene for high-rate supercapacitors

Graphene is a type of promising electrode material for high-energy and high-power density supercapacitors,but its electrochemical performance is greatly limited by the restacking problem.In this work,we reported a facile approach to synthesis graphene with chemically bonded vanadium oxide(VOx)nanoparticles and demonstrated that chemically-bonded VOxnanoparticles can effectively prevent the graphene sheets from restacking and hence improve the electrochemical performance.The capacitance of VOxbonded graphene increases to 272 F/g compared to 183 F/g of pristine graphene in 1 M H3PO4 aqueous electrolyte at 2 A/g.The VOx-bonded graphene also showed improved rate capability in both H3PO4 and ionic liquid electrolytes.The capacitance retention increases to 54.5%from 28.5%at 100 A/g(compare to2 A/g)in H3PO4 and increases to 65.1%from 46.3%at 2 A/g(compare to 0.2 A/g)in neat ionic liquid.A high energy density of 84.4 Wh/kg is obtained within the voltage window of 4 V in ionic liquid.Even at a high-power density of 1000 W/kg,the VOx-bonded graphene shows a high energy density of 47.3 Wh/kg.

Increased utilization and mass activity of PtRu on reduced graphene oxide by heat treatment of its aerogel followed by composite with nanomaterials

The method to increase PtRu utilization and its catalytic activity of PtRu nanoparticles supported on reduced graphene oxide(RGO)by avoiding its restacking was proposed with the aim of developing an active catalyst for a direct methanol fuel cell.The heat treatment at 200◦C of the GO aerogel(GOA)prepared by freeze drying of GO ice was introduced to weaken the attractive force of the hydrogen bonding between the GO sheets followed by the composite with the nanoparticles,i.e.,ketjenblack(KB),TiO_(2)and Ti_(4)O_(7),at different weight ratios.The catalyst supported on the heat-treated GOA(RGOA),PtRu/RGOA,improved the PtRu utilization to some extent and also increased the ECSA and mass activity compared to that of PtRu/RGO.RGOA had fewer oxygen functional groups,especially the epoxy groups.Due to the treatment and composite,the PtRu utilization was increased from 66.5%for PtRu/RGO to 128.6%for PtRu/RGOA+Ti_(4)O_(7)(4:1)and the mass activity was improved from 50.7 A/g-PtRu for PtRu/RGO to 130.5 A/g-PtRu for PtRu/RGOA+Ti_(4)O_(7)(1:1).The Ti_(4)O_(7)nanoparticles showed the best catalytic performance for the composite suggesting that the strong interaction between Ti_(4)O_(7)and the Pt nanoparticles was effective due to its high electronic conductivity.