Electrostatic self-assembly combined with microwave hydrothermal strategy: construction of 1D/1D carbon nanofibers/crystalline g-C3N4 heterojunction for boosting photocatalytic hydrogen production

g-C3N4 (CN) has been widely explored as a visible light photocatalyst. Nevertheless, the low structural ordering of CN suffers from high-density defects that resulting in poor charge separation efficiency. Therefore, increasing the crystallinity of CN is considered to be an efficient approach to enhance its photocatalytic activity. However, crystalline g-C3N4 (CCN) synthesized via ionothermal method exhibits one-dimensional (1D) nanorod structure and is prone to agglomerate due to its high surface energy, giving rise to unsatisfactory performance improvement. Herein, the 1D carbon nanofibers/crystalline g-C3N4 heterojunction photocatalyst (CNF/CCN) is obtained through electrostatic self-assembly combined with microwave heating strategy. The CNF/CCN sample shows an enhanced photocatalytic H2 evolution rate (HER) of 6398 µmol g−1 h−1, which is up to 16.0 and 2.6 times of CN and CCN, respectively. The enhanced HER performance of CNF/CCN is attributed to the improved crystallinity of CN, promoted visible light utilization, large specific surface area and efficient charge transfer across the interface between CNF and CCN. This work conveys a simple and general method for crystallinity and activity enhancement for a wide range application of CN.