Aggrandizing the Photoactivity of ZnO Nanorods toward N2 Reduction and H2 Evolution through Facile In Situ Coupling with NixPy

Abstract

The photocatalytic water and nitrogen reduction in the presence of solar light gives rise to an alternative route for sustainable green energy. This novel approach can resolve the difficulty of greenhouse gas emanation from fossil fuels and global warming and energy crisis. Making headway for developing more robust and efficient photocatalytic systems still remains an enormous challenge toward industrial usage on a large scale. To meet this challenge, herein we report hydrothermally prepared ZnO nanorods (NRs) coupled with nickel phosphide (NiₓPy) via a low-temperature phosphidation method. NiₓPy acts as a robust co-catalyst, which increases the visible light absorption efficacy and photocatalytic performance of ZnO NRs toward nitrogen reduction and hydrogen evolution. The nanorod morphology of the ZnO-NiₓPy hybrid is revealed by transmission electron microscopy (TEM) analysis while the formation of the Ni–P moiety and its interaction with ZnO NRs are verified by X-ray photoelectron spectroscopy (XPS) analysis. Besides, the excellent photogenerated charge separation and transfer efficiency are further confirmed using photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and transient analysis, which are the main aspects for activity enhancement in the nickel phosphide-modified ZnO NRs. The optimized ZnO-NiₓPy nanocomposite exhibits an outstanding ammonia production rate of 2304.43 μmol h–¹ g–¹ without using any organic scavenger or precious noble metal. On the other hand, this catalyst also exhibits stupendous performance with a H₂ generation rate of 10 481 μmol h–¹ g–¹ using methanol as a hole scavenger. This magnificent result can be attributed to (i) Ni–P sites acting as active reaction sites for nitrogen and proton adsorption and activation, (ii) efficacious charge carrier segregation, and (iii) proficient charge transfer to the surface of nickel phosphide. This finding offers a new avenue for developing noble metal-free phosphide-based hybrids toward highly efficient photocatalytic reactions.