Low-temperature growth of graphene/WC/W₂C 2D heterostructures via hot-wire chemical vapor deposition: structural, optical, and electrochemical properties

Due to the recent increasing demand for the use of two-dimensional (2D) materials in energy-related applications, such as electrode for supercapacitors, batteries, thermoelectric devices, and hydrogen production via water-splitting, the production of high-quality 2D materials has become more challenging at the research and development level. These materials mainly graphene, transition metal dichalcogenides, transition metal nitrides and carbides, and MXenes—possess fascinating physical and electrical properties, high yield and large surface area, making them very important core elements in the near future of nanotechnology. In this work, large-area graphene nanoflakes (few-layer and multi-layer) directly fabricated on tungsten nanoparticles (W NPs)-coated c-Si and quartz substrates by hot-wire chemical vapor deposition (HWCVD) at low substrate temperatures (<500 ℃). An argon plasma pretreatment was employed to form W NPs, which serve as a metal catalysts to facilitate the growth of large-area few-layer or multi-layer graphene nanoflakes. Ultrathin WC/W₂C nanosheets were assembled beneath the graphene nanoflakes, forming graphene/WC/W₂C heterostructures that exhibited excellent optical transparency (> 80%), high electrical conductivity, and a remarkable photocurrent density (~ 2 mA cm⁻² at 1.5 V vs. Ag/AgCl) under visible-light irradiation. These results demonstrate the potential of HWCVD-grown graphene/WC/W₂C heterostructures as efficinent photoelctrode materials for hydrogen production through water-splitting process.