Temperature differentiated synthesis of hierarchically structured N,S-Doped carbon nanotubes/graphene hybrids as efficient electrocatalyst for hydrogen evolution reaction

Abstract The development of carbon-based catalysts with excellent activity for hydrogen evolution reaction (HER) is highly desirable but still remains a significant challenge. Chemical doping and morphology engineering are paramount to enhance their catalytic performance toward HER. Herein, we present a novel and effective strategy to synthesize heteroatoms-doped three-dimensional (3D) carbon nanotubes/graphene hierarchical architecture (N,S-CNTs/N,S-G) on layered double oxide substrates, in which the N,S-doped CNTs are in-situ grown on both sides of N,S-doped graphene, by two differentiated chemical vapor deposition (CVD) processes. The high concentrations of N and S dopants (up to 6.5 at.%) provide sufficient catalytic active sites for HER, while the CNTs seamlessly grafted on graphene ensure the excellent electric conductivity of N,S-CNTs/N,S-G hybrids. Consequently, the 3D N,S-CNTs/N,S-G composites display superior electrocatalytic activity for HER with an onset potential of 62 mV vs. RHE (achieve current density of 1 mA cm−2) and a small overpotential of 126 mV at 10 mA cm−2, which outperforms most of reported chemical doped carbon-based composites. The synthetic strategy facilitates the fabrication of other heteroatoms-doped 3D electrochemical catalysts.