N-doped graphene grown on silk cocoon-derived interconnected carbon fibers for oxygen reduction reaction and photocatalytic hydrogen production

Carbon-based metal-free catalysts are a promising substitute for the rare and expensive platinum (Pt) used in the oxygen reduction reaction. We herein report N-doped graphene (NG) that is exquisitely integrated into highly conductive frameworks, simultaneously providing more active sites and higher conductivity. The NG was in situ grown on carbon fibers derived from silk cocoon (SCC_f) using a simple one-step thermal treatment. The resulting product (NG-SCC_f), possessing a meso-/macroporous structure with three-dimensional (3D) interconnected networks, exhibits an onset potential that is only 0.1 V less negative than that of Pt/C and shows stability and methanol tolerance superior to those of Pt/C in alkaline media. Moreover, in the absence of Pt as co-catalyst, NG-SCC_f shows a photocatalytic H₂ production rate of 66.0 μmol·h^–1·g^–1, 4.4-fold higher than that of SCC_f. This outstanding activity is intimately related to the in situ grown NG, hierarchically porous structure, and 3D interconnected networks, which not only introduce more active sites but also enable smooth electron transfer, mass transport, and effective separation of electron-hole pairs. Considering the abundance of the green raw material in combination with easy and low-cost preparation, this work contributes to the development of advanced sustainable catalysts in energy storage/conversion fields, such as electro- and photocatalysis.