Carbon cloth (CC) supported core–shell NiCo 2 O 4 @MnMoO 4 nanoarrays composite is successfully synthesized by two-step hydrothermal method, and used as binder-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). In comparison with the NiCo 2 O 4 /CC, MnMoO 4 /CC, CC and Pt CEs, the NiCo 2 O 4 @MnMoO 4 /CC CE exhibits the significantly improved electrochemical performance. And the improved electrochemical performance can be attributed to the contribution from CC combination outer-sphere MnMoO 4 nanosheet and inner-sphere NiCo 2 O 4 nanowires array, which offer a large electrochemical surface area, good electrochemical activity to iodide/triiodide couple, and lower charge-transfer and series resistances. The DSSCs device assembled with core–shell composite NiCo 2 O 4 @MnMoO 4 /CC CE achieved excellent power conversion efficiency of 11.87%, which is higher than that of counter parts of NiCo 2 O 4 /CC (10.97%), MnMoO 4 /CC (11.08%), CC (4.84%) and Pt (8.55%) CEs. Also, the NiCo 2 O 4 @MnMoO 4 /CC based device remains 90.9% efficiency up to 10 days under ambient conditions. Therefore, the NiCo 2 O 4 @MnMoO 4 /CC composite with unique structure can be further developed as an efficient and cost-effective metal oxides electrocatalysts in DSSCs and other related fields.
Chunyu Cui,Jiantie Xu,Lei Wang,Di Guo,Minglei Mao,Jianmin Ma,Taihong Wang
Three-dimensional heterostructured NiCo2O4@MnMoO4 nanocolumn arrays (NCAs) on Ni foam were first fabricated through an improved two-step hydrothermal process associated with a successive annealing treatment. The hybrid NiCo2O4@MnMoO4 electrode exhibited remarkable pseudocapacitor property with high initial mass specific capacitance of 1705.3 F g–1 at 5 mA cm–2, and retained 92.6% after 5000 cycles, compared to the bare NiCo2O4 electrode with 839.1 F g–1 and 90.9%. The excellent capacitive property of the NiCo2O4@MnMoO4 hydrid was attributed to its high-electron/ion-transfer rate, large electrolyte infiltrate area, and more electroactive reaction sites.
Ying Xue,Zhengjie Xie,Xilong Liu,Liangyu Liu,Yixin Li,Yingjie Hua,Xudong Zhao,Xiaoyang Liu
Hierarchical core-shell heterostructured NiCo 2 O 4 @MnMoO 4 nanosheet hybrid arrays were successfully synthesized on nickel foam via a facile two-step hydrothermal reaction followed by a calcination process. The highly porous hierarchical core-shell heterostructure was fabricated by preforming a NiCo 2 O 4 nanosheet “core” as a substrate and then guiding the ultrathin MnMoO 4 nanosheet “shell” onto its surface. The growth thickness of ultrathin MnMoO 4 nanosheets was controlled by adjusting the hydrothermal reaction time. The optimized core-shell heterostructured NiCo 2 O 4 @MnMoO 4 electrode exhibited a specific capacity of 1205.75 C g −1 at a current density of 1 mA cm −2 in 2 M KOH solution and displayed outstanding cycling stability with a capacity retention rate of 100.49% after 5000 charge-discharge cycles at a current density of 30 mA cm −2 . An asymmetric supercapacitor (ASC) device was assembled using the optimal NiCo 2 O 4 @MnMoO 4 nanosheet hybrid arrays as the positive electrode and activated carbon (AC) as the negative electrode which achieved a maximum energy density of 39.04 W h kg −1 at a power density of 156.86 W kg −1 and retained 34.12 W h kg −1 even at the high power density of 1568.74 W kg −1 . In addition, the ASC device presented an excellent cycling performance, maintaining 95.00% retention of its initial specific capacitance after 10,000 cycles at a current density of 20 mA cm −2 , demonstrating its promising potential in energy storage.
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