A hierarchical 2D Ni-Mo-S nanosheet@nitrogen doped graphene hybrid as a Pt-free cathode for high-performance dye sensitized solar cells and fuel cells

A novel hybrid of 2D Ni-Mo-S nanosheet integrated nitrogen doped graphene (NG) is successfully developed via a simple, scalable, and cost-effective hydrothermal process, and its application towards energy conversion devices is explored. The presence of exclusive mesoporous structures combined with an excellent conducting NG network in the Ni-Mo-S/NG hybrid exhibits superior electrocatalytic activities as a counter electrode (CE) for dye-sensitized solar cells (DSSCs) and the oxygen reduction reaction (ORR) in alkaline electrolytes. SEM and TEM studies demonstrate the uniform anchoring of ultra-thin Ni-Mo-S nanosheets on NG networks. The hierarchical Ni-Mo-S/NG hybrid outperformed Ni-Mo-S, NG, and Pt when used as a CE in DSSCs and showed excellent ORR activity. The power conversion efficiency (PCE) of DSSCs with the Ni-Mo-S/NG hybrid as the CE achieved 9.89%, outperforming conventional Pt CEs (8.73%). Furthermore, Ni-Mo-S/NG showed high catalytic activity for the ORR with an onset of 0.98 V_RHE and outstanding durability compared to commercial Pt/C. The present study demonstrates the unique role of integrated Ni-Mo-S nanosheets anchored NG towards I₃^- reduction and the ORR, and demonstrates an efficient strategy for designing highly catalytically active and cost-effective electrocatalysts for DSSC and fuel cell applications.