CuCr_2O_4@rGO Nanocomposites as High-Performance Cathode Catalyst for Rechargeable Lithium–Oxygen Batteries

Rechargeable lithium–oxygen batteries have been considered as a promising energy storage technology because of their ultra-high theoretical energy densities which are comparable to gasoline. In order to improve the electrochemical properties of lithium–oxygen batteries(LOBs), especially the cycling performance, a high-efficiency cathode catalyst is the most important component.Hence, we aim to demonstrate that CuCr_2O_4@rGO(CCO@rGO) nanocomposites, which are synthesized using a facile hydrothermal method and followed by a series of calcination processes, are an effective cathode catalyst. The obtained CCO@rGO nanocomposites which served as the cathode catalyst of the LOBs exhibited an outstanding cycling performance for over 100 cycles with a fixed capacity of 1000 mAh g^(-1) at a current density of 200 mA g^(-1). The enhanced properties were attributed to the synergistic effect between the high catalytic efficiency of the spinel-structured CCO nanoparticles, the high specific surface area, and high conductivity of the rGO.

In situ confined vertical growth of Co_(2.5)Ni_(0.5)Si_(2)O_(5)(OH)_(4)nanoarrays on rGO for an efficient oxygen evolution reaction

Rational design of oxygen evolution reaction(OER)catalysts at low cost would greatly benefit the economy.Taking advantage of earth-abundant elements Si,Co and Ni,we produce a unique-structure where cobalt-nickel silicate hydroxide[Co_(2.5)Ni_(0.5)Si_(2)O_(5)(OH)_(4)]is vertically grown on a reduced graphene oxide(rGO)support(CNS@rGO).This is developed as a low-cost and prospective OER catalyst.Compared to cobalt or nickel silicate hydroxide@rGO(CS@rGO and NS@rGO,respectively)nanoarrays,the bimetal CNS@rGO nanoarray exhibits impressive OER performance with an overpotential of 307 mV@10 mA cm^(-2).This value is higher than that of CS@rGO and NS@rGO.The CNS@rGO nanoarray has an overpotential of 446 mV@100 mA cm^(-2),about 1.4 times that of the commercial RuO_(2)electrocatalyst.The achieved OER activity is superior to the state-of-the-art metal oxides/hydroxides and their derivatives.The vertically grown nanostructure and optimized metal-support electronic interactions play an indispensable role for OER performance improvement,including a fast electron transfer pathway,short proton/electron diffusion distance,more active metal centers,as well as optimized dualatomic electron density.Taking advantage of interlay chemical regulation and the in-situ growth method,the advanced-structural CNS@rGO nanoarrays provide a new horizon to the rational and flexible design of efficient and promising OER electrocatalysts.

1T-VSe_(2)@rGO复合材料的设计合成及其在镁电中的应用

本文采用简单的一步水热法合成了1T-VSe_(2)@rGO复合材料,在APC电解液环境下,并将其作为第二代可充电镁离子电池的正极材料。测试结果显示,1T-VSe_(2)@rGO复合正极材料在50 mA g^(-1)下具有263 mAh g^(-1)的高可逆容量,在50 mA g^(-1)下连续循环100次,可获得91%的初始电容的优秀循环寿命。因此,1T-VSe_(2)@rGO作为正极材料在镁离子和其他可充电电池中的应用打开了新的思路。

Modulating of MoSe_(2)functional plane via doping-defect engineering strategy for the development of conductive and electrocatalytic mediators in Li-S batteries

The lithium polysulfide shuttle and sluggish sulfur reaction kinetics still pose significant challenges to lithium-sulfur(Li-S)batteries.The functional plane of Fe-MoSe_(2)@r GO nanohybrid with abundant defects has been designed and applied in Li-S batteries to develop the functional separator and multi-layer sulfur cathode.The cell with a functional separator exhibits a retention capacity of 462 m Ah g^(-1)after the 1000th at 0.5 C and 516 m Ah g^(-1)after the 600th at 0.3 C.Even at low electrolyte conditions(7.0μL_(mgsulfur)^(-1)and 15μL_(mgsulfur)^(-1))under high sulfur loadings(3.46 mg cm^(-2)and 3.73 mg cm^(-2)),the cell still presents high reversible discharge capacities 679 and 762 m Ah g^(-1)after 70 cycles,respectively.Further,at sulfur loadings up to 8.26 and 5.2 mg cm^(-2),the cells assembled with the bi-layers sulfur cathode and the tri-layers sulfur cathode give reversible capacities of 3.3 m Ah cm^(-2)after the 100th cycle and 3.0 m Ah cm^(-2)after the 120th cycle,respectively.This research not only demonstrates that the FeMoSe_(2)@r GO functional plane is successfully designed and applied in Li-S batteries with superior electrochemical performances but also paves the novel way for developing a unique multi-layer cathode technique to enhance and advance the electrochemical behavior of Li-S cells at a high-sulfur-loading cathode under lean electrolyte/sulfur(E/S)ratio.

A novel synthesis of Nb_(2)O_(5)@rGO nanocomposite as anode material for superior sodium storage

The development of novel anode materials,with superior rate capability,is of utmost significance for the successful realization of sodium-ion batteries(SIBs).Herein,we present a nanocomposite of Nb_(2)O_(5)and reduced graphene oxide(rGO)by using hydrothermal-assisted microemulsion route.The water-in-oil microemulsion formed nanoreactors,which restrained the particle size of Nb_(2)O_(5)and shortened the diffusion length of ions.Moreover,the rGO network prevented agglomeration of Nb_(2)O_(5)nanoparticles and improved electronic conductivity.Consequently,Nb_(2)O_(5)@rGO nanocomposite is employed as anode material in SIBs,delivering a capacity of 195 mAh/g after 200 charge/discharge cycles at 0.2 A/g.Moreover,owing to conductive rGO network,the Nb_(2)O_(5)@rGO electrode rende red a specific capacity of 76 mAh/g at high current density of 10 A/g and maintained 98 mAh/g after 1000 charge/discharge cycles at 2 A/g.The Nb_(2)O_(5)@rGO electrode material prepared by microemulsion method shows promising possibilities for application of SIBs.

Mn3O4 nanoparticles@reduced graphene oxide composite:An efficient electrocatalyst for artificial N2 fixation to NH3 at ambient conditions

Currently,industrial-scale NH3 production almost relies on energy-intensive Haber-Bosch process from atmospheric N2 with large amount of CO2 emission,while low-cost and high-efficient catalysts are demanded for the N2 reduction reaction (NRR).In this study,Mn3O4 nanoparticles@reduced graphene oxide (Mn3O4@rGO) composite is reported as an efficient NRR electrocatalyst with excellent selectivity for NH3 formation.In 0.1 M Na2SO4 solution,such catalyst obtains a NH3 yield of 17.4 μg·h^-1·mg^-1cat.and a Faradaic efficiency of 3.52% at-0.85 V vs.reversible hydrogen electrode.Notably,it also shows high electrochemical stability during electrolysis process.Density functional theory (DFT) calculations also demonstrate that the (112) planes of Mn3O4 possess superior NRR activity.

Visualization of the electrocatalytic activity of three- dimensional MoSe2@reduced graphene oxide hybrid nanostructures for oxygen reduction reaction

Developments of nanostructured transition metal dichalcogenides （TMDs） materials as novel electrocatalyst candidates for oxygen reduction reaction （ORR） is a new strategy to promote the developments of non-precious metal ORR catalysts. In this work, a three-dimensional （3D） hybrid of rosebud-like MoSe2 nanostructures supported on reduced graphene oxide （rGO） nanosheets was successfully synthesized through a facile hydrothermal strategy. The prepared MoSe2@rGO hybrid nanostructure showed enhanced electrocatalytic activity for the ORR in alkaline medium compared to that of the pure MoSe2, rGO, and their simple physical mixture, which could benefit from the excellent oxygen adsorption ability of the abundantly exposed active edge sites of the ultrathin MoSe2 layers, the conductivity and aggregation-limiting effect of the rGO platform, as well as the unique 3D rosebud-like architecture of the hybrid material. The electrocatalytic activity of the MoSe2@rGO hybrid towards ORR was comparable to that of com- inertial Pt/C catalysts. And the promoted reaction was revealed to involve a nearly four-electron-dominated ORR process by analysis of the obtained Koutecky- Levich plots. The scanning electrochemical microscopy （SECM） technique, with the advantages of investigating of the local catalytic activity of samples with high spatial resolution and simultaneously evaluating activities of different catalysts in a single experiment, was further applied to investigate the local ORR electrocatalytic activity of MoSe2@rGO and compare it with those of other catalyst samples through applying different sample potentials. The excellent stability and methanol tolerance of the 3D nanostructured MoSe2@rGO hybrid against methanol further prove the 3D nanostructured MoSe2@rGO hybrid as a promising ORR electrocatalyst in alkaline solution for potential applications in fuel cells and metal-air batteries.