Synthesis of Ni₃Bi₂S₂ Coupled with N-Doped Carbon Sheets as Electrocatalyst for Triiodide and Oxygen Reduction

Herein, we report a novel composite structure consisting of Ni₃Bi₂S₂ particles coupled with N-doped carbon (NC) sheets. Different from the generally used high vacuum or microwave-assisted technologies, metal-rich Ni₃Bi₂S₂ can be successfully synthesized via a simple pyrolysis procedure, with NC employed as a reducing agent. In addition, the phase purity, size, and dispersity of the Ni₃Bi₂S₂ particles, which were encapsulated by the NC shell, were modulated by the content of NC. The X-ray photoelectron spectroscopy (XPS) analysis demonstrated the metallic state of the Ni and Bi elements, which ensured good Ni₃Bi₂S₂ electrical conductivity. As a result, the resultant Ni₃Bi₂S₂/NC (0.55 II) catalyzed triiodide reduction with a lower charge transfer resistance than commercial Pt/C (1.4 II). Moreover, Ni₃Bi₂S₂/NC catalyzed the oxygen reduction reaction with a positive ORR half-wave potential (0.81 V vs. RHE) and a low Tafel slope (47 mV dec^-1). Our study thus provides the novel exploration of the electrochemical performance of Ni₃Bi₂S₂ and indicates its promising application in electrocatalytic reactions.