Co_xMo_(1−x)S₂ intermixed reduced graphene oxide as efficient counter electrode materials for high-performance dye-sensitized solar cells

In this study, nanocomposite electrocatalysts composed of cobalt molybdenum sulfide flower-like nanosheets intermixed with reduced graphene oxide (Co_xMo_(1−x)S₂/rGO) were prepared by a facile one-step hydrothermal method and were used to prepare counter electrodes (CE) of high-performance dye-sensitized solar cells (DSSCs). The structural and morphological analysis of the nanocomposites were carried out using field emission scanning electron microscopy, micro-Raman, and X-ray photoelectron spectroscopies, which revealed 2-dimensional petal-like nanosheets of the ternary metal sulfides intermixed with the reduced graphene oxide sheets. The DSSCs fabricated using Co_xMo_(1−x)S₂/rGO (CMS-2/rGO) as the counter electrode material exhibited power conversion efficiency (PCE) of 9.04%, which was found to be superior to the PCEs of DSSCs with CEs made of MoS₂/rGO (7.56%), Co_xMo_(1-x)S₂ (7.04–7.78%), and conventional Pt (8.72%). The electrochemical measurements showed that the excellent electrocatalytic activity of the Co_xMo_(1−x)S₂/rGO on I₃^- can be attributed to the expanded active sites, improved charge transfer across the CE, and reduced electrode/electrolyte interface resistance. The facile preparation approach and outstanding catalytic behavior of Co_xMo_(1−x)S₂/rGO indicate that the nanostructured Co_xMo_(1-x)S₂/rGO intermix would be a cost-effective material over the platinum used in the CE of DSSCs.