Facile Aqueous Route to Large-Scale Superhydrophilic TiO₂-Incorporated Graphitic Carbon Nitride-Coated Ni(OH)₂ and Ni₂P Nano-Architecture Arrays as Efficient Electrocatalysts for Enhanced Hydrogen Production

Water splitting by an electrochemical method to generate hydrogen gas is an economic and green approach to resolve the looming energy and environmental crisis. Designing a composite electrocatalyst having integrated multichannel charge separation, robust stability, and low-cost facile scalability could be considered to address the issue of electrochemical hydrogen evolution. Herein, we report a superhydrophilic, noble-metal-free bimetallic nanostructure TiO₂/Ni₂P coated on graphitic polyacrylonitrile carbon fibers (g-C/TiO₂/Ni₂P) using a facile hydrothermal method followed by phosphorylation. In an aqueous-based route, PAN is dissolved in water in the presence of ZnCl₂, followed by wet-spinning to prepare scalable PAN/ZnCl₂ fibers. The nitrogen-contained porous graphitic carbon fibers are prepared via the pyrolysis of PAN/ZnCl₂ fibers; now ZnCl₂ acts as a volatile porogen to form porous matrix structures. Finally, the as-prepared graphitic carbon fibers are electrochemically activated by incorporating TiO₂/Ni₂P active sites. The materials formed in this work show excellent electrocatalytic activity for the hydrogen evolution reaction. The as-synthesized g-C/TiO₂/Ni₂P catalyst shows a low overpotential, its electrocatalytic activity is improved, and its efficiency is better than that of the commercial Pt/C catalyst. At a current density of -10 mA/cm², the g-C/TiO₂/Ni₂P catalyst shows an overpotential of 55 mV, while the commercial Pt/C catalyst shows an overpotential of 77 mV. Our work provides a facile aqueous scalable route with no need for noble metals that can be considered as a potential alternative for the commercial Pt/C catalyst.