Controllable Synthesis of Metallic Ni3P–Ni Spheres on Graphitic Carbon Nitride Nanosheets to Promote Photocatalytic Hydrogen Generation

To achieve the construction of efficient photocatalytic H 2 generation systems, developing highly active and durable earth-abundant H 2 generation cocatalyst is still a challenge. In this paper, we construct a noble-metal-free Ni 3 P–Ni composite, which displays strong chemical stability and high-efficiency as a cocatalyst to enhance the visible-induced photocatalytic activities in H 2 generation of g-C 3 N 4 . Ni 3 P–Ni/g-C 3 N 4 is prepared by one-step annealing of amorphous Ni–P nanoparticles and g-C 3 N 4 . The result verifies that both Ni 3 P and metallic Ni worked as electron cocatalysts and significantly enhanced the visible light H 2 generation over g-C 3 N 4 . The optimum composite 2.0 wt.% Ni 3 P–Ni/g-C 3 N 4 exhibits a high H 2 generation rate of 203.3 μmol g −1 h −1 , which is 1.6, 2.7, and 53.5 times as much as those obtained on Ni 3 P/g-C 3 N 4 , Ni/g-C 3 N 4 , and pure g-C 3 N 4 respectively. Photoluminescence and photoelectrochemical analysis confirm that the metallic Ni plays multifunctional roles in boosting the H 2 generation under visible light, which could both accept the photo-generated electrons from g-C 3 N 4 and enhance the electron transfer to Ni 3 P for further H 2 generation. This investigation provides a route to the rational design and development of earth-abundant metal phosphide and metal composites, which could be utilized as noble-metal-free cocatalysts for the improvement of H 2 generation activity. Graphic Abstract Spherical Ni 3 P–Ni particles with metallic Ni spread over the inner and outer surface of Ni 3 P sphere was synthesized and hybrid with g-C 3 N 4 . The specific structure of spherical Ni 3 P–Ni leads to adequate contact area between ternary Ni 3 P, Ni, and g-C 3 N 4 . Ni with high electrical conductivity could act as an electron transfer bridge between g-C 3 N 4 and Ni 3 P, leading to effective charge separation and enhanced photocatalytic hydrogen generation.