Role of defects and oxygen-functional groups in carbon paper cathode for high-performance direct liquid fuel cells

Abstract

A facile and scalable approach to modify electrodes with achieving excellent performance and low-cost is urgently needed for direct liquid fuel cells (DLFCs). A carbon paper (CP) electrode with porous carbon nanosheets is successfully fabricated by electrochemical exfoliation to enhance the charge transfer and increase reaction sites in DLFCs. After in-situ electrochemical exfoliation for 4 min, the carbon fiber surface becomes porous and rough to enlarge specific surface area and produce abundant defects for the electrode, greatly increasing reaction active sites. In addition, massive oxygen functional groups are introduced to significantly improve the reaction kinetics and wettability of the electrode. The exfoliated CP shows superior electrocatalytic activity with minimum overpotential and highest reduction reaction rate, benefitting from the larger specific surface area, abundant defects, and superhydrophilic property. Moreover, the exfoliated CP without catalysts is directly used as the cathode for a membraneless DLFC with sodium persulfate as an oxidant to yield outstanding performance. The peak power density of the DLFC with the exfoliated CP is 188.6 mW cm−2, 93.4% higher than that with the pristine CP. Results show that a feasible way to acquire excellent cell performance and low cost is obtained by electrochemically exfoliated CP electrode for DLFCs.