Polyaniline induced multi-functionalities in interfacially coupled electrocatalysts for hydrogen/oxygen evolution reactions

Abstract

Tuning the catalytic surface as well as interface of the electrocatalysts is central to the rational design of efficient electrocatalysts for hydrogen/oxygen evolution reactions (HER/OER). Herein, we report a polyaniline (PANi) driven interface engineering approach to synthesize molybdenum disulfide (MoS₂) and nickel iron layered double hydroxide (NiFeLDH) grown carbon fiber (CF) based electrocatalysts for the HER and OER, respectively. The interfacial PANi layer improves the coupling adhesion between the electrocatalysts and CF, which strongly influences the charge transfer kinetics as well as structural integrity of the overall catalyst. In addition, the intimate connection induces large vacancies in both MoS₂ and NiFeLDH catalysts. More specifically, PANi layers effectively capture the intermediate H⁺ ions and promote their reduction to hydrogen molecules. With these remarkable characteristics, MoS₂@PANi-CF delivered impressive HER activity with a low Tafel value of 35, 40, and 31 mV dec⁻¹, in acidic, alkaline, and neutral electrolytes, respectively, surpassing that of the commercial Pt@C catalyst. Similarly, the NiFeLDH@PANi-CF catalysts manifested excellent OER efficiency with a low overpotential of 170 mV at 100 mA cm⁻² and Tafel value of 47 mV dec⁻¹ in an alkaline medium and an overpotential of 310 mV at 50 mA cm⁻² and Tafel value of 76 mV dec⁻¹ in an acidic medium. Impressively, these electrocatalysts demonstrated outstanding durability for as long as 48 h for the HER and 100 h for the OER with negligible degradation.