Novel platinum-bismuth alloy loaded KTa0.5Nb0.5O3 composite photocatalyst for effective nitrogen-to-ammonium conversion.

A novel heterojunction composite BiPt/KTa0.5Nb0.5O3 (KTN) was designed and synthesized through a combination of hydrothermal and precipitation procedures. Bi and Pt contents were optimized. The best 1 %Bi-0.25 %Pt/KTN sample presented better photocatalytic performance in ammonia synthesis than KTN, 1 %Bi/KTN, and 0.25 %Pt/KTN. Under simulated sunlight, the NH3 generation rate of the best BiPt/KTN reached 6.3 times that of pure KTN. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) analysis revealed that BiPt alloy nanoparticles were formed and decorated on the surface of KTN nanocubes. The PtBi alloy provided an appropriate Schottky barrier with a height between those of Pt/KTN and Bi/KTN. The barrier can efficiently capture photogenerated charge carriers while also preventing their backflow and recombination. Thus, the PtBi/KTN presented the best capability in charge separation, thereby displaying the highest photocatalytic activity in the N2-to-NH3 reaction. Additionally, the loaded BiPt alloy also broadened the photoresponse of KTN to the visible light region via its surface plasmon resonance effect, which was another reason for the increased photoactivity. This study not only provided a potential photocatalyst for photocatalytic nitrogen fixation but also showed new ideas for the design of highly efficient catalysts via bimetal alloy modification.