Ultrathin bismuth oxyiodide nanosheets for photocatalytic ammonia generation from nitrogen and water under visible to near-infrared light

Abstract

Artificial photosynthesis of ammonia using atmospheric nitrogen and water is a sustainable but challenging alternative to the Haber-Bosch process. Bismuth oxyiodide (BiOI) is a promising candidate due to its superior light absorption capability (bandgap of around 1.8 eV) and abundant surface oxygen vacancies. However, its improper band edge positions made it inactive for overall water-splitting and N2 fixation. In this work, ultrathin BiOI nanosheets were synthesized through a simple surfactant (PVP) assisted hydrothermal route. The nanosheets split pure water into H2 and O2 and converted nitrogen and water into ammonia under visible or near-infrared light. PVP capping not only reduced the thickness of BiOI sheets but also upshifted its band edge positions due to the surface electric dipole induced by polyvinyl pyrrolidone molecules on the BiOI surface, thus enabling the water oxidation and nitrogen reduction half reactions simultaneously.