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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]

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 seek a Pt‐free carbon material counter electrode for dye‐sensitized solar cells (DSSCs), the electrocatalytic activity of needle coke (NC) for the reduction of triiodide in DSSCs was investigated, and further improved by decorating with Ni to prepare Ni decorated needle coke (Ni‐NC) via a one‐step solid‐state synthesis method. It is found that the NC is a potential carbon counter electrode material for DSSCs due to its high‐density anisotropy with considerable conductivity. Although the decoration of Ni may sacrifice certain conductivity of NC, the electrocatalytic activity of Ni‐NC towards reduction of triiodide was better than that of NC. To obtain a balanced point of conductivity and electrocatalytic performance for Ni‐NC, the loading amount of Ni together with the solid‐state synthesis conditions were also studied. It is indicated that these parameters also have some effect on the performance of Ni‐NC. Under the optimized conditions, the DSSCs based on Ni‐NC counter electrode achieve an 77 % higher energy conversion efficiency of 4.39 % than that of NC counter electrode (2.48 %), and comparable to the value (5.34 %) obtains with Pt counter electrode. It is an efficient way to improve the performance of NC by decorating with Ni via a facile solid‐state synthesis method, and promote the application of needle coke as carbon counter electrode materials in DSSCs. [ABSTRACT FROM AUTHOR]