Bimetallic Ni-Fe-S nanoparticles directly grown on porous MXene substrate as bifunctional electrocatalyst for water electrolysis

초록

Among the various renewable energy sources, hydrogen (H2) is considered as most promising substance in future energy society owing to its high energy density and environmental friendliness. Recently, electrochemical water splitting, which is consisted of anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER), has great potential for high-purity hydrogen production. However, the practical efficiency of water electrolysis is limited due to the intrinsically sluggish reaction kinetics of OER and HER. To date, the precious metal-based electrocatalysts such as RuO2 and Pt/C were employed as state-of-the-art electrocatalysts forwater electrolysis. However, due to the high expense, mono-functionality, and unsatisfactory stability of them, research on bifunctional electrocatalysts with low cost and high activity has become an urgent topic. In this work, 2D-structured titanium carbide (Ti3C2) MXene was employed as an efficient substrate for growth of active species with plentiful terminal groups (-OH, -O, -F). The MXene has outstanding hydrophilicity and electrical conductivity, leading to the enhanced electrocatalytic activity in aqueous alkaline solution. To improve electrochemical surface area and introduce channels for mass transport, we generated abundant pore in 2D-structured Ti3C2 substrate. Additionally, the insufficient redox property of the Ti3C2 was improved via direct growth of Ni-Fe-S with atomic ratio of Ni:Fe=3:1 using one-step solvothermal process. As a result, the prepared electrocatalyst exhibited excellent electrocatalytic activity with low overpotential of 309 and 148 mV at 10 mA cm?1 for OER and HER, respectively. Additionally, the Ni-Fe-S/porous-MXene showed exceptional stability during the continuous water electrolysis for 100 h.