二硒化铁/还原氧化石墨烯的制备及其在染料敏化太阳能电池中的应用

通过水热反应合成出二硒化铁/还原氧化石墨烯(FeSe₂/rGO)复合材料, 并将其作为对电极材料应用于染料敏化太阳能电池(DSSC). 利用X射线衍射、拉曼光谱、场发射扫描电子显微镜和高分辨透射电子显微镜对FeSe₂/rGO的结构和形貌进行了表征. 利用循环伏安法、电化学阻抗谱和Tafel曲线测试分析了FeSe₂/rGO对电极的电催化活性. 结果表明: FeSe₂呈纳米棒结构, 长度在100-200 nm之间, 且紧密地附着在rGO 的表面, FeSe₂/rGO对电极对I₃^-的还原具有很好的催化活性. 电池的J-V曲线测试显示: 基于FeSe₂/rGO对电极的DSSC的转换效率达到了8.90%, 相比基于单纯的FeSe₂对电极的DSSC(7.91%)和rGO对电极的DSSC(5.24%)都有了显著提高, 甚至优于铂对电极的DSSC(8.52%).

Preparation of iron diselenide/reduced graphene oxide composite and its application in dyesensitized solar cells

In recent years, dye-sensitized solar cells (DSSCs) have attracted much attention because of their easy fabrication, good flexibility low cost and relatively high efficiency. As a crucial component, the function of counter electrode (CE) is to collect the electrons from external circuits and transfer them to electrolyte by catalyzing the reduction of I₃^- into I^-. Platinum (Pt) is a conventional material of CE in DSSCs due to its high conductivity and outstanding catalytic activity towards the reduction of triiodide (I₃^-). However, the high cost and low abundance of Pt restrict the commercial application of DSSCs. Moreover, Pt could be dissolved slowly in the I^-/I₃^- redox electrolyte, which will deteriorate the long term stability of DSSCs. Therefore, it is necessary to explore novel material with high conductivity, catalytic activity and stability to replace Pt. In this paper, with Fe(NO₃)₃·9H₂O and graphene oxide (GO) serving as raw materials and deionized water as the solvent, we synthesize iron diselenide (FeSe₂) nanorods (with diameters in a range of about 100-200 nm)/reduced graphene oxide (rGO) composite through a facile hydrothermal method and use the composite as CE material of DSSCs for the first time. The structure and morphology of FeSe₂/rGO are characterized by using X-ray diffraction (XRD), Raman spectrum, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The XRD pattern shows that the FeSe₂ is typically orthorhombic phase. The SEM images show that the FeSe₂ has a structure of nanonods and can be attached to the surface of rGO closely The surface of FeSe₂/rGO composite is rough and exhibits a porous structure. The TEM image shows that the FeSe₂ has a high degree of crystallinity and orientation. To evaluate the catalytic activity and conductivity of FeSe₂/rGO, we perform cyclic voltammetry (CV) measurements, electrochemical impedance spectroscopy and obtain Tafel polarization curves for FeSe₂/rGO electrode and also for Pt, FeSe₂ and rGO electrodes for comparison. The results indicate that the CE based on FeSe₂/rGO composites has the lowest peak-to-peak voltage separation (E_{pp}) charge transfer resistance (R_ct) and series resistance (R_s) in the four different CEs, suggesting that the FeSe₂/rGO CE has an excellent electrocatalytic performance for the reduction I₃^-. The current density-voltage (J-V) curves of DSSCs with different CEs under the illumination of 1 sun (100 mW ·cm^-2) show that the cell with FeSe₂/rGO CE has an open-circuit voltage (V_oc) of 0.727 V, a short-circuit current (J_sc) of 18.94 mA ·cm^-2, a fill factor (FF) of 0.65 and an excellent power conversion efficiency (PCE) of 8.90%, which is a notable improvement compared with the PCE of the cell with an FeSe₂ CE (7.91%) and an rGO CE (5.24%). It can be attributed to the synergetic effects between the FeSe₂ nanorods and rGO which eventually improve the PCE of DSSC We also conducte the experiments on the electrochemical stability of FeSe₂/rGO CE by sequential CV measurements the result indicates that the FeSe₂/rGO composite has a better stability than Pt in I^-/I₃^- electrolyte In summary, we synthesize a novel FeSe₂/rGO conductive catalyst. This hybrid material possesses the features of FeSe₂ and rGO, exhibiting both highly catalytic activity and high conductivity Therefore, the low-cost and high-performance FeSe₂/rGO composite can be a promising CE material to replace Pt in the large-scale industrial production of DSSCs.