Synergistic activation of bimetallic sulfides via hierarchical architecture: a superior bifunctional electrocatalyst...

The development of cost-effective and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) and iodine reduction reaction (IRR) is critical for advancing sustainable energy conversion technologies. Herein, we report a hierarchical zero-dimensional/three-dimensional FeS₂/CoS₂@nitrogen-doped carbon (NC) composite synthesized via sulfur-assisted modification. This unique architecture integrates bimetallic FeS₂ and CoS₂ active sites with a NC framework, enabling strong electronic coupling, abundant active site exposure, and enhanced charge transfer kinetics. As an IRR electrocatalyst for solar cell applications, the FeS₂/CoS₂@NC-based device achieves a power conversion efficiency of 8.34 %, outperforming the conventional Pt-based counter electrode (7.17 %). Moreover, an impressive indoor photovoltaic efficiency of 18.26 % is achieved under low-light conditions. Electrochemical analyses reveal that FeS₂/CoS₂@NC exhibits a low overpotential of 117 mV at 10 mA cm^-2 and a small Tafel slope of 62 mV dec^-1 for the HER, along with excellent long-term durability. This superior electrocatalytic performance is attributed to the synergistic interaction between FeS₂ and CoS₂, which modulates the electronic structure and optimizes the adsorption energies, while the conductive NC matrix facilitates efficient electron transport and enhances structural stability. This study offers a viable design strategy for the construction of bifunctional, non-precious-metal-based electrocatalysts with significant potential for advanced energy conversion and storage applications.