Effect of phosphating on NiAl-LDH layered double hydroxide form S-scheme heterojunction for photocatalytic hydrogen evolution

NiAl-LDH was completely phosphate to obtain Ni2P with strong adsorption characteristics, and a simple physical stirring method was used to fix Ni2P in the 3D layered double hydroxide NiAl-LDH layer to obtain a new type of Ni2P@NiAl-LDH (NNP) S-scheme heterojunction catalyst. The Ni2P obtained by phosphating process can provide 3D reaction sites for photoelectrons and absord photogenerated carriers to participate in the photocatalytic reaction. Moreover, the S-scheme interface heterojunction can directionally change the transfer path of electric charges and improve the effective utilization of electrons. The hydrogen evolution test results show that the hydrogen production of the composite material NNP-3 (Ni2P-15%@NiAl-LDH) within 5 h can reach 107.62 μmol (2152.4 μmolg−1 h−1), 17.27 times and 2.59 times of NiAl-LDH and Ni2P, respectively. And after 25 h hydrogen production cycle, the composite catalyst still has a high hydrogen production rate and showed strong stability. Optical tests show that the composite material Ni2P@NiAl-LDH (NNP) has a strong visible light capturing ability and can increase the absorption range of visible light. Photochemical tests show that the use of Ni2P to modify NiAl-LDH can reduce the overpotential of hydrogen evolution, accelerate the transfer of photoelectrons and improve the utilization of electrons. This research provides a new idea for improving the performance of NiAl-LDH using the phosphating process, and provides an effective method for NiAl-LDH to participate in the photocatalytic hydrogen evolution technology with high efficiency.