Visible-light responsive gold nanoparticle and nano-sized Bi2O3–x sheet heterozygote structure for efficient photocatalytic conversion of N2 to NH3

Abstract

The advancement in catalysis techniques for sustainable environmental applications, particularly an alternative to the current Haber-Bosch process for NH₃, has recently gained widespread attention. Although photocatalytic conversion of N₂ to NH₃ using solar energy is an eco-friendly method, it has the limitation of low quantum yield. Recently, 2D Bi-based photocatalysts which exhibit higher visible light absorption than TiO₂ and higher stability than MXene have been an active research topic, and their performance can be enhanced through improved visible light absorption properties by incorporating plasmonic gold nanoparticles while nitrogen adsorption could be enhanced through oxygen vacancy (OV) processes. In the present study, we explore the application of 2D nano-sized Bi₂O_3–x and gold nanoparticles for visible light photo generation of NH₃. HRTEM and XPS reveal that the formation of AuNP and nano-sized Bi₂O_3–x in AuNP/Bi₂O_3–x heterozygote structure promotes the charge carrier mobility and charge transport at the interface, resulting in a 2.6-fold increase in the photocatalytic activity compared to micro-sized Bi₂O_3–x with AuNP. The improved photocatalytic performance can be ascribed to significant enhancement of visible light absorption by plasmonic nanoparticles, fast charge transport and mobility (due to sheet morphology) and the N₂ activation by OV in AuNP/Bi₂O_3–x heterozygote. Through a systematic experimental investigation involving catalysts, concentration, pH, and scavengers, the highest photocatalytic performance was achieved with the heterozygote structures of AuNP/n-Bi₂O_3–x under optimized conditions, yielding 432.5 μmol g_cat⁻¹ h⁻¹ of NH₃.