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In order to obtain inexpensive Pt-free counter electrode materials for dye-sensitized solar cells and expand the application fields of low-rank coal, lignite-based Ni/C composite was prepared by low-medium temperature pyrolysis method using Huolinhe lignite as raw materials. The structure and chemical components of as-synthesized lignite-based Ni/C composite was characterized by XRD, FT-IR, TG, Raman, SEM, TEM, and XPS, and the electrocatalytic activity of lignite-based Ni/C composite counter electrode was investigated by cyclic voltammetric curve, electrochemical impedance spectrum, and Tafel polarization curve. It is found that the electrocatalytic activity of the lignite was improved after low-medium temperature pyrolysis and composited with Ni species to form lignite-based Ni/C composite, which helps to catalyze the reduction of electrolyte and thus improve the photoelectric conversion efficiency of the solar cells. The photoelectric conversion efficiency (η) of the dye-sensitized solar cells based on the lignite-based Ni/C composite counter electrode was 3.42% (Jsc = 11.49 mA cm−2, Voc = 0.75 V, FF = 0.40) significantly higher than that of the lignite counter electrode (η = 0.20%, Jsc = 3.16 mA cm−2, Voc = 0.72 V, FF = 0.09). This indicates that low-medium temperature pyrolysis and composition with Ni are an effective method to improve the photovoltaic performance of lignite-based counter electrode materials. The lignite-based Ni/C composite was synthesized and applied in counter electrode for DSSCs. [ABSTRACT FROM AUTHOR]

To improve the photovoltaic performance of the traditional TiO 2 photoanode for dye-sensitized solar cells (DSSCs), a series of layered TiO 2 /rGO composited DSSCs photoanode was assembled by changing the morphologies of the TiO 2 and introducing reduced graphene oxide (rGO) into different areas of the photoanode films. Firstly, TiO 2 nanoflowers (TiO 2 -NFs), TiO 2 nanorods (TiO 2 -NRs) were prepared employing the hydrothermal method and used as photoanode materials to explore the synergistic effect of TiO 2 with different morphologies in layered photoanode. Then, TiO 2 -NFs/rGO composited photoanode (TNF/rGO) were fabricated to research the mechanism of rGO on improving electron transmission in the layered photoanode. The effect of adding rGO at different parts of the layered photoanode on the performance of DSSCs was also investigated. Attributing to the enhancement of light absorption and charge transfer, a champion power conversion efficiency (η) of 9.21 % (J sc = 23.36 mA cm−2, V oc = 0.74 V, FF = 0.53) was achieved with the layered TiO 2 /rGO composited photoanode containing two consecutive layers of TiO 2 -NFs/rGO and P25/rGO, which exhibited an 82.01 % increase than traditional TiO 2 (pure P25) photoanode (η = 5.06 %, J sc = 12.09 mA cm−2, V oc = 0.73 V, FF = 0.58). It is an effective way to design and fabrication of layered TiO 2 /rGO composited photoanode to regulate the photovoltaic performance of traditional TiO 2 photoanode for DSSCs based on the synergistic effect of its multi-layer structure, TiO 2 morphologies and introduction of rGO. [Display omitted] • Layered TiO 2 /rGO photoanode was constructed by TiO 2 with different morphologies and reduced oxide graphene. • The dye loading, light utilization and charge transfer of TiO 2 photoanode were improved in layered TiO 2 /rGO photoanode. • Layered photoanode with rGO exhibits improved electron transfer and smaller charge recombination. • Compared with P25 photoanode, the cell efficiency based on the layered TiO 2 /rGO composited photoanode increased by 82.01 %. [ABSTRACT FROM AUTHOR]

In the field of dye‐sensitized solar cells (DSSCs), although Pt is commonly used as counter electrode materials owing to its great electrocatalytic activity and conductivity, the high price and small reserves of Pt limit its large‐scale application. In this paper, heteromorphic Ni decorated Fe‐containing carbon nanofibers (Ni/NiO@Fe‐CNFs) was prepared by a thermal synthesis method, and applied as composite counter electrode materials for DSSCs. It was found that the as‐synthesized Ni/NiO@Fe‐CNFs shows better electrocatalytic activity than that of Fe‐CNFs and CNFs for the reduction reaction of triiodide to iodide. The improved electrocatalytic activity is not only attributed to the introduction of Fe2O3 to form Fe‐CNFs, but also attributed to the heteromorphic Ni decoration and their synergistic effect. The photoelectric conversion efficiency of DSSCs with Ni/NiO@Fe‐CNFs counter electrode is 4.81 %, much higher than that of CNFs (0.62 %) and Fe‐CNFs counter electrode (3.65 %), and comparable to the value of Pt counter electrode (5.10 %). Accordingly, the Ni/NiO@Fe‐CNFs is expected to be a potential counter electrode material to replace Pt. [ABSTRACT FROM AUTHOR]

To screen out suitable electrode materials and overcome the shortcomings of the existed electrode materials for the application in dye-sensitized solar cells and supercapacitors, NiS 2 /reduced graphene oxide (NiS 2 /rGO) composite material was prepared by a simple one-step hydrothermal method in this paper and applied in the field of both dye-sensitized solar cells and supercapacitors as electrode material. In an electrolyte of 6 M KOH, the NiS 2 /rGO composite material with bilayer capacitance characteristics exhibited a high specific capacitance of 259.20 F g−1 at the current density of 0.6 A g−1, which was significantly higher than that of rGO (188.94 F g−1). Moreover, at a current density of 2 A g−1, the NiS 2 /rGO composite material had 92.85% capacitance retention after 2000 cycles. When applied as counter electrode material for the dye-sensitized solar cells, the NiS 2 /rGO composite material counter electrode exhibited a satisfactory photoelectric conversion efficiency (η) of 3.16% under standard simulated sunlight (AM 1.5 G), which was significantly higher than that of single rGO counter electrode (improved by 90.40%). The NiS 2 /rGO composite electrode material prepared by a simple one-step hydrothermal method is a potential bi-functional composite electrode materials for both dye-sensitized solar cells and supercapacitors. [Display omitted] • NiS 2 /reduced graphene oxide composite was prepared by one-step hydrothermal method. • NiS 2 /reduced graphene oxide exhibits excellent electrochemical performance. • High photoelectric conversion efficiency was obtained for dye sensitized solar cells. • Excellent specific capacitance and durability were obtained for supercapacitors. [ABSTRACT FROM AUTHOR]