石墨烯氧化程度对Ni(OH)2赝电容性能的影响

基于密度泛函理论(DFT)设计了一系列不同氧化程度的还原氧化石墨烯片(rGNOs)并研究了其表面的氧化缺陷与吸附的氢氧化镍(Ni(OH)₂)之间的相互作用. 结果发现，rGNOs表面的含氧基团与Ni(OH)₂之间的吸附能与含氧基团的氧化程度相关. 在吸附Ni(OH)₂后，rGNOs的原子间距和电荷分布的变化也都受rGNOs表面的含氧缺陷的氧化程度影响. 理论计算的结果与实验观察的结果一致并能给出合理的解释.我们用简单的恒电位电化学沉积法有效地在rGNOs表面制备了粒径只有5 nm的Ni(OH)₂纳米粒子. 在Ni(OH)₂/rGNOs制备过程中，氧化石墨烯的电化学还原是关键步骤. Ni(OH)₂上吸附的Ni(OH)₂因具有更高的吸附能而使其与在镍膜表面直接吸附的Ni(OH)₂(在5 mV·s^-1下比电容为656 F·g^-1)相比具有更高的比电容值(在5 mV·s^-1下为1591 F·g^-1).rGNOs在吸附Ni(OH)₂后构型和电荷分布的变化导致Ni(OH)₂具有更低的等效串联电阻和更佳的频率响应.Ni(OH)₂/rGNOs优异的赝电容特性表明其有潜力成为新型赝电容器材料.

Influence of Graphene with Different Oxidation Degrees on Nickel Hydroxide Pseudocapacitor Characterization

We designed a series of models of reduced graphene oxide sheets (rGNOs) with different oxidation degrees and then studied the interactions between oxidation defects on rGNOs and nickel hydroxide (Ni(OH)₂) using density functional theory (DFT). The adsorption energy between the oxygen-containing groups on rGNOs and Ni(OH)₂ is dependent on the oxidation degree of rGNOs. The variations of atomic distances and charge distribution of the oxide-defected graphene after absorbing Ni(OH)₂ suggested that the oxygen-containing groups on rGNOs improve the characteristics of Ni(OH)₂ as a pseudocapacitor. These theoretical results agree well with available experimental observations and give an explanation for some experimental results. We also introduce a simple potentiostatic electrodeposition method, with which Ni(OH)₂ nanoparticles about 5 nm in diameter were effectively dispersed on the substrate via induction of oxidation defects on rGNOs. In the fabrication of Ni(OH)₂/rGNOs, electrochemical reduction of graphene oxide is the key process. The stronger adsorption results in Ni(OH)₂/rGNOs have higher rate pseudocapacitance (1591 F·g^-1 at 5 mV·s^-1) compared with that of Ni(OH)₂ on bare nickel (656 F·g^-1 at 5 mV·s^-1). The variations of the geometries and charge distributions of the rGNOs after absorbing Ni(OH)₂ lead to the lower equivalent series resistance and better frequency response of Ni(OH)₂/rGNOs than Ni(OH)₂/Ni. The high capacitance of Ni(OH)₂/rGNOs indicates that Ni(OH)₂/rGNOs have the potential of being used as the electrode material of pseudocapacitors.