▎ 摘　　要

Flexible photofuel cells (PFCs) have triggered strong scientific interest as promising emerging energy conversion devices for clean power generation due to their potential advantages in low-cost, simple fabrication, room-temperature operation, and high conversion efficiency, etc. However, how to enable a PFC with excellent structural flexibility and robustness, and meanwhile with sufficient fuel fed onto electrodes and therefore high power generation remains a significant challenge. Herein, a high-performance coaxial cable-shaped PFC device is successfully designed and integrated by employing wet-spun graphene fiber as the inner cathode, TiO2 nanoparticle-intercalated graphene spring as the outer photoanode, and a robust polymer gel coated in-between as the electrolyte separator. The as-fabricated fiber-shaped PFC demonstrates effective adsorption of fuel, essential light penetration, and rapid electron/ion transport. Importantly, the fiber cells are sensitive to methane-based mine gas under sunlight, exhibiting a photocurrent density nearly three orders of magnitude higher than that in air, and excellent and reliable photovoltaic performance with a maximum power density of 0.04 W cm(-2) at 0.35 V. This work has shed light not only in using cheap mine gas for efficient power generation, but also on new strategies for design and fabrication of high-performance PFCs in flexible electronic devices.