Great enhancement of electrochemical cyclic voltammetry stabilization of Fe3O4 microspheres by introducing 3DRGO

Excellent electrochemical stabilities and superior electrocatalytic activities of inexpensive counter electrodes (CEs) play an essential role in the large-scale practical application of dye-sensitized solar cells (DSSCs). Herein, the spherical Fe3O4 was selected as a CE and high power conversion efficiency (PCE) of 8.76% was achieved, which was more than Pt's efficiency (7.80%). Unfortunately, the efficiency decreased expeditiously (from 8.76% to 7.88%) in three consecutive measurements. Cyclic voltammetry (CV) tests also reveal that the Ox1 and Red1 peaks of the CE disappear after a few cycles, which could be attributed to the fact that pure Fe3O4 was easily corroded in the electrolyte, and the catalytic activity was gradually lost after repeated tests. Here, a novel strategy is that Fe3O4 spheres are encapsulated within the 3D reduced graphene (3DRGO) networks to enhance the stability of CV. Three consecutive photovoltaic measurements demonstrate that PCE of the cell with Fe3O4@3DRGO nanocomposites as CE has been enhanced and the cell shows surprising stabilization (PCE = 9.10%, 9.07% and 9.05% in the three consecutive tests, respectively). The specific surface area of the composite is increased after introducing 3DRGO, which is helpful for electrons transferring rapidly from external circuit to the system of redox to catalytically reduce triiodide, and also decreases charge-transfer resistance. This work not only achieves the outstanding photovoltaic performance and stabilization, but also offers a promising strategy in constructing 3D nanomaterials with novel structure for wide energy applications.