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 Ni3P-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-C3N4. Ni3P-Ni/g-C3N4 is prepared by one-step annealing of amorphous Ni-P nanoparticles and g-C3N4. The result verifies that both Ni3P and metallic Ni worked as electron cocatalysts and significantly enhanced the visible light H-2 generation over g-C3N4. The optimum composite 2.0 wt.% Ni3P-Ni/g-C3N4 exhibits a high H-2 generation rate of 203.3 mu mol g(-1) h(-1), which is 1.6, 2.7, and 53.5 times as much as those obtained on Ni3P/g-C3N4, Ni/g-C3N4, and pure g-C3N4 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-C3N4 and enhance the electron transfer to Ni3P 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 Spherical Ni3P-Ni particles with metallic Ni spread over the inner and outer surface of Ni3P sphere was synthesized and hybrid with g-C3N4. The specific structure of spherical Ni3P-Ni leads to adequate contact area between ternary Ni3P, Ni, and g-C3N4. Ni with high electrical conductivity could act as an electron transfer bridge between g-C3N4 and Ni3P, leading to effective charge separation and enhanced photocatalytic hydrogen generation.

Automated summary

This study successfully developed a noble-metal-free Ni3P-Ni cocatalyst to enhance the visible-induced photocatalytic activities in H-2 generation of g-C3N4. The metallic Ni in Ni3P-Ni plays multifunctional roles in boosting the H-2 generation under visible light by accepting photo-generated electrons from g-C3N4 and enhancing electron transfer to Ni3P for further H-2 generation. This provides a new pathway for the rational design and development of earth-abundant metal phosphide and metal composites for improved H-2 generation activity.