Fabrication of Hierarchically Porous Silicon Carbonitride/Nickel Nanocomposite Using Branch-Structured Polysilazane as a Hydrogen Evolution Reaction Catalyst

Hierarchically porous silicon carbonitride/nickel (SiCN/Ni) nanocomposites for a catalyst of the hydrogen evolution reaction (HER) were fabricated using branch-structured polysilazane with phenyl substitution, phenylsilsesquiazane (PSSQZ), and nickelocene (NiCp₂) as a precursor. The Ni nanoparticles are uniformly distributed in the SiCN matrix due to coordination between amine groups of PSSQZ and NiCp₂. Hierarchical pore structure provided a path through which H₂ outgas can diffuse as well as increase active sites where HER can occur due to its large surface area. As a result, the overpotential of 10 mA/cm² of the hierarchically porous SiCN/Ni nanocomposite decreased from 540 to 390 mV. In addition, the multiwalled carbon nanotubes (MWCNTs) produced by the catalytic reaction of NiCp₂ lowered the charge transfer resistance to 133 Ω. Furthermore, the fabricated hierarchically porous SiCN/Ni nanocomposite showed stable performance and long-term durability in acidic environments for 100 h because of the high corrosion resistance of the SiCN matrix.