Synthesis of lignite-based Ni/C composite with low-medium temperature pyrolysis method as an efficient Pt-free counter electrode for dye-sensitized solar cells

Abstract

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 counter electrode materials were prepared by low-medium temperature pyrolysis method using Huolinhe Lignite as raw material. The structure and chemical components of as-synthesized lignite-based Ni/C composite counter electrode materials were characterized by XRD, FT-IR, TG, Raman, SEM, TEM and XPS, and the electrocatalytic activity of lignite-based Ni/C composite counter electrode were investigated by cyclic voltammetric curve, electrochemical impedance spectrum, 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 composites, which helps to catalyze the electrolyte reduction and thus improve the photoelectric conversion efficiency of the cell. The photoelectric conversion efficiency (η) of 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 is an effective method to improve the photovoltaic performance of coal-based counter electrode materials.