CVD-grown three-dimensional sulfur-doped graphene as a binder-free electrocatalytic electrode for highly effective and stable hydrogen evolution reaction

Three-dimensional sulfur-doped graphene (3DSG) with high sulfur-doping content (2.9%) was synthesized on nickel foam by chemical vapor deposition using solid organic source of thianthrene as both the carbon source and sulfur dopant. The 3DSG further treated by Ar plasma (3DSG-Ar) was demonstrated as a free-standing and binder-free electrocatalyst without any polymeric binders for electrode fabrication. Particularly, 3DSG-Ar can be used as highly effective and stable electrocatalyst for hydrogen evolution reaction (HER). It delivers a very low Tafel slope of 64 mV dec−1, which is superior or comparable to most metal-free carbon-based electrocatalysts ever reported; moreover, it shows superior long-term electrocatalytic stability even after 2000 cycles. The excellent HER performances of 3DSG-Ar can be attributed to its well-designed porous, conductive and flexible 3D sulfur-doped graphene structure. Sulfur doping combing with plasma treatment cause a synergistic effect to effectively provide many more electrocatalytic active sites, resulting in significantly improved HER performance. In addition, the conductive, porous and flexible 3D graphene skeleton can not only act as free-standing and binder-free electrocatalytic electrode, but also guarantee the interconnected conductive paths in the whole electrode, leading to facilitate the charge transportation between the electrocatalyst and electrolyte and thus enhance its HER performances.