Phosphide protected FeS2 anchored oxygen defect oriented CeO2NS based ternary hybrid for electrocatalytic and photocatalytic N2 reduction to NH3

Abstract

The Haber–Bosch process enables the industrial production of NH₃ from N₂ and H₂, it represents a high energy consumption route and also releases a large amount of anthropogenic CO₂. However, solar light mediated N₂ photoreduction through a semiconductor photocatalyst is a green and sustainable route, which could help to suppress global warming and serve as an attractive hydrogen fuel storage medium. Herein, we have synthesized a phosphide protected FeS₂–FeP–CeO₂NS ternary nanohybrid through a simple hydrothermal method followed by a sulfidation–phosphidation technique. The physicochemical and morphological properties of the synthesized materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The optimum CPS3 nanohybrid exhibits a remarkable ammonia evolution rate of up to 5.6 mmol h⁻¹ g⁻¹ under mild reaction conditions and without using any precious noble metal or organic scavengers. The obtained results were superior to those obtained from recently reported hybrid materials. The main reason for the high photofixation may be because: (i) the O_v/Ce³⁺ and Fe–P act as active sites for nitrogen adsorption and activation; and (ii) the photoelectrons are well separated and transfer to the activated N₂ and the overall kinetic study reveals the two electron proton coupled reduction reaction. This work gives some insightful and significant information about the construction and selection of earth abundant photocatalysts for use in the ideal solar driven nitrogen reduction reaction (NRR).