Highly efficient p-type Cu3P/n-type g-C3N4 photocatalyst through Z-scheme charge transfer route

Phosphides exhibit relatively low overpotential for electrical hydrogen evolution reaction (HER), thus they have great potential to be used for cocatalyst for photocatalyst. Cu3P, as a p-type semiconductor, tends to form a p-n junction with an n-type photocatalyst. Typically, it is treated as a sensitizer to extend the light absorption. However, its function and work mechanism are not fully understood in the catalyst system. In this report, we synthesized g-C3N4 and loaded Cu3P nanoparticle on its surface. The photoluminescence (PL) spectra, photocurrent and electrochemical impedance spectra confirm the Cu3P greatly enhance the charge separation process. Electrochemical HER results indicate that the composites have lower over-potential for HER. These results confirm the Cu3P works as a cocatalyst in the system, not a sensitizer. Further, we tracked the photogenerated electron transfer direction via photodeposition of Pt nanoparticles. The Pt nanoparticles tend to deposit near the Cu3P nanoparticles. That illustrates the photogenerated electron will be left on Cu3P nanoparticles. On the other hand, the photocatalytic decomposition of Rhodamine B (RhB) illustrates that the holes are left on the g-C3N4 due to both g-C3N4 and Cu3P/g-C3N4 have similar decomposition rate, but the Cu3P cannot decompose RhB. Based on these, we proposed the photogenerated electron of g-C3N4 recombine with the hole of Cu3P, the photogenerated electron of Cu3P will be left for HER. That reasonably explain the cocatalyst function of Cu3P in the composite catalyst system.