Onion-like graphitic carbon covering metallic nanocrystals derived from brown coal as a stable and efficient counter electrode for dye-sensitized solar cells

Abstract

A graphitic carbon matrix decorated with highly dispersed metallic nanocrystals and ash components is fabricated via a facile self-sacrificed template strategy derived from brown coal. The variation of the morphology and structure, as well as the influence of annealing temperature and acid treatment of coal-derived catalysts on the electrocatalytic activity are investigated. The as-made Coal-800 counter electrode with robust structural stability shows remarkable photovoltaic and electrocatalytic performance, achieves a high power conversion efficiency of 9.03%, which is superior to that of Pt counter electrode (8.24%). The synergistic effect of the heteroatom-doped Coal-800 catalyst containing the ash components and Ca nanocrystals endows this graphitic carbon covering structure with outstanding catalytic performance, which may be the active species for the triiodide reduction reaction. This work not only demonstrates that brown coal-derived composite is a strong candidate to solve the issues related with the Pt counter electrode for dye-sensitized solar cells but also sheds light on the exploration of low-cost and highly efficient electrocatalysts that can be applied to energy-related applications.