Construction of NiO/Ag/g-C3N4 nanosheet: Enhanced photocatalytic H2 evolution by the unique structure and synergistic effect of Ag and NiO

In this work, NiO/Ag/g-C3N4 hybrids with unique structure were designed and fabricated by a stepwise photoreduction and thermal treatment method. Herein, under the effect of electrostatic attraction, the NiO was mainly deposited on the surface of Ag quantum dots in the NiO/Ag/g-C3N4 hybrids (denoted as NACN-x, x was the mole ratio of NiO and Ag). Under visible light irradiation, the H2 evolution rate of the optimized hybrid NACN-1 was about 586 μmol•h−1•g−1. However, in the same conditions, the g-C3N4 had negligible H2 evolution property. Furthermore, in comparison with the other contrast materials, the H2 evolution rate of NACN-1 was about 3.5, 2.5 and 1.4 times than that of Ag/g-C3N4, NiO/g-C3N4 and NiO-Ag/g-C3N4 (prepared via one-step photoreduction method). According to the results of the optical-electrical property tests, characterizations of TEM and XPS, and theoretical calculation, the superior H2 evolution property of NACN-1 should profit from the unique structure and synergistic effect of NiO and Ag. Because the Ag quantum dots in NiO/Ag/g-C3N4 hybrid would act as electron trapping center to significantly improve the separation efficiency of photoexcited carriers. Meanwhile, the electrons would be consumed on the reactive sites of the close contacted NiO to produce H2.