Abstract: Graphene fiber material is one type of macroscopically one-dimensional materials assembled by graphene building blocks or coating graphene on other fibrous building blocks. The typical graphene fiber materials can be classified into graphene fiber and graphene-coated hybrid fiber based on their different building blocks. This type of materials exhibits superior tensile strength, excellent electrical and thermal conductivities, making them favorable for applications in flexible energy storage devices, electromagnetic shielding and wearable electronics. Recently, the chemical vapor deposition (CVD) method, conventionally used for fabricating film-like graphene, has been widely applied to the synthesis of graphene fiber materials. For preparing graphene fiber, the use of CVD method can prevent the complicated and time-consuming reducing treatment of graphene oxide (GO), which is well known as an imperative step in the commonly used wet spinning method. For preparing graphene-coated hybrid fiber, the CVD method can achieve an efficient modulation of graphene quality, and ensure a strong adhesion between graphene and fibrous substrates. In this review, we summarized the CVD methods for fabricating graphene fiber materials, including graphene-assembled graphene fiber and graphene-coated hybrid fiber, and introduced their excellent mechanical, electrical, thermal and optical properties along with their broad applications in intelligent sensors, optoelectronic devices, and flexible electrodes. Furthermore, the challenges in synthesizing CVD-fabricated graphene fiber materials were also analyzed. This review can be briefly divided into three parts:(1) Synthesis of graphene fibers:Up to now, the CVD method is a feasible and effective way to synthesize graphene with high crystallinity. The CVD strategies for fabricating graphene fibers mainly consist of the template method, the secondary growth method, and the film-scrolling method, which can simplify the fabrication process and efficiently modulate graphene quality. (2) Synthesis of graphene glass fibers:Similar to graphene growth directly on non-catalytic glass surfaces, CVD method can also be applied to synthesize graphene on glass fibers. By modifying the experimental parameters (carbon source, pressure, temperature, etc.), high-quality graphene films with controllable thickness can be uniformly coated on glass fibers. Meanwhile, the as-fabricated graphene glass fiber can be further used as a high-performance flexible electrode, electro-optic modulator, or electrocatalyst. (3) Synthesis of graphene metal fibers:Graphene can be controllably grown on metal fibers using the CVD method. Compared to the bare metal fiber, the fabricated graphene metal fiber exhibited enhanced electrical and thermal conductivities as well as better chemical stability, which can expand its applications in ultra-thin electronics and high-power circuits.

Key words: Chemical vapor deposition, Graphene fiber, Graphene glass fiber, Graphene metal fiber