Preparation And Electrochemical Performance Of Hybrid Holey Graphene Aerogel Composites

Nowadays,due to the fast consumption of fossil fuels(oil,coal,etc.)and tremendous serious environmental issues,the demand for high performance energy-storage devices has been increasing dramatically.Graphene aerogel(GA)is identified as an ideal electrode material due to its excellent electrochemical performance.Moreover,since graphene oxide(GO)has many functional groups,it can be combined with other materials to further improve its electrochemical performance.In this paper,hydrophilic carbon black/hybrid holey graphene aerogels have been successfully prepared by hydrothermal method.The hydrophilic carbon black is distributed on the graphene sheets in a string or spherical shape.Such structure can not only prevent the compact restack of graphene sheets,but also provide rapid diffusion path for more edge plane participation in doublelayer capacitance.Next,the layered double hydroxide(LDH)is loaded on the optimal ratio of hydrophilic carbon black/hybrid holey graphene aerogels.Finally,systematic research is done on these materials in supercapacitor and capacitive deionization.The research contents are as follows:1.GO is prepared by improved hummers method,and the holey graphene oxide(HGO)is synthesized by etching with hydrogen peroxide.Then HGO is mixed with GO in different mass ratios to prepare hybrid holey graphene aerogel(HGA-n)by hydrothermal method.Electrochemical studies exhibit that HGA-3(the mass ratio of HGO to GO is 6:4)has the highest specific capacitance of 379 F g-1 at a current density of 0.1 A g-1.Compared with GA,the specific capacitance is improved by about 89%.Then,hydrophilic carbon black is loaded on HGA-3.HGAC-2(the mass ratio of(HGO+GO)to hydrophilic carbon black is 4)displays the highest specific capacitance of 438 F g-1 at a current density of 0.1 A g-1,which is about 13%higher than HGA-3.In addition,the specific capacity retention of HGAC-2 is about 92.6%after 5000 cycles at a current density of 10 A g-1.As the electrode material for capacitive deionization,the salt adsorption capacity of HGAC-2 is 49.85 mg g1 under the conditions of 1.2 V and an initial concentration of 800 mg L-1 NaCl solution,which is about 16%higher than HGA-3 electrode(43.04 mg g-1).Moreover,the maximum ion removal rate of HGAC-2 is 2.69 mg g-1 s-1 as the NaCl concentration is 1600 mg L-1,which is about 67%higher than HGA-3(1.61 mg g-1 s-1).2.The NiCo-LDH/hybrid holey graphene aerogel composites(NiCoLDH-n)are successfully prepared using the hydrophilic carbon black/hybrid holey graphene aerogel as the matrix by hydrothermal method.The structure characterization exhibits that NiCo-LDH-1 and NiCo-LDH-2 have a composite structure with flowers on the graphene sheets.Electrochemical tests exhibit that NiCo-LDH-2 has the best electrochemical performance.At a scan rate of 1.0 mV s-1,the specific capacitance of NiCo-LDH-2 can reach 747 F g-1,which is 23%and 62%higher than NiCo-LDH(608 F g-1)and HGAC-2(461 F g-1),respectively.In addition,the specific capacity of NiCo-LDH-2 decreases by only 8.7%after 5000 cycles at a current density of 10 A g-1.In the capacitive deionization test,the NiCo-LDH-2 displays a salt adsorption capacity of 61.99 mg g-1 under the conditions of 1.2 V and an initial concentration of 800 mg L-1 NaCl solution,which is about 2.43 times higher than NiCo-LDH(18.09 mg g1).Moreover,the maximum ion removal rate of NiCo-LDH-2 is 38.68 mg g-1 min-1.