B doped C3N4 enhancement built-in electric field and coupling NiS to construct interfacial electric field for boosting photogenerated carrier separation to enhance hydrogen evolution

• B-doped to enhance the BIEF and coupling with NiS to form an IEF promote the separation of photogenerated carriers. • The best photocatalytic performance of 20NiBCN is 4294.1 μmol g -1 h −1 , which is 3903.7 times higher than CN. • A possible mechanism for enhanced photocatalytic hydrogen production in the presence of a double electric field. Due to the weak electric field (EF), g-C 3 N 4 (CN) exhibits rapid recombination of photogenerated charge carriers, resulting in low photocatalytic hydrogen evolution. This work promotes photogenerated carrier separation by doping B into the CN cell to enhance the built-in electric field (BIEF) and coupling with NiS to form an interfacial electric field (IEF). The KPFM characterisation results show that the B doping CN (BCN) surface energy is enhanced from 0.821 to 0.924 V, and the surface potential of NiS-loaded BCN (NiBCN) is further increased from 0.924 to 0.986 V. These results illustrate the enhancement of the BIEF and the successful construction of the IEF. With the action of the dual electric fields, the photogenerated carrier separation of NiBCN composites is accelerated. The TPR spectra shows that the photocurrent of 20NiBCN increases from 0.15 and 0.25 to 0.6 μA/cm 2 compared with original CN and BCN, respectively. The photocatalytic performance of 20NiBCN is significantly improved by the dual electric fields, with the optimal hydrogen production efficiency reaching 4294.1μmol g -1 h −1 , which is 61.1, 3903.7 and 6134.4 times as much as BCN, CN and NiS respectively. The study offers a new perspective on the development of double electric field effect catalysts.