Z-scheme K-C3N4/Ag/Ag3PMo12O40 heterojunction with improved visible light photodegradation of formaldehyde

Photocatalytic degradation of formaldehyde is an ideal way to solve indoor air pollution. The development of Z-scheme heterojunction photocatalysts is economic and effective way in eliminating formaldehyde pollution. Herein, a ternary heterojunction photocatalyst K-C3N4/Ag/Ag3PMo12O40 (abbreviated as K-C3N4/Ag/APM) was synthesized by self-assembly of PMo12O403- with Ag+ and K-C3N4 followed by in-situ photoreduction. The Ag/Ag3PMo12O40 (APM) hetero-nanoparticles obtained by photoreduction are uniformly loaded on K-C3N4 nanosheets. The structure, morphology, optical and photoelectrochemical properties etc. of K-C3N4/Ag/APM were characterized and explored. The photocatalytic activity of K-C3N4/Ag/APM was assessed on the degradation of HCHO. K-C3N4/Ag/APM showed remarkably improved photocatalytic activity than the g-C3N4, K-C3N4 and K-C3N4/Ag in the degradation of HCHO under visible light irradiation. The K-C3N4/Ag/APM heterojunction can degrade 60% gaseous HCHO (0.16 mg L-1) in 60 min (lambda > 400 nm). The optimum experimental parameters were temperature 20 degrees C, RH 70%, catalyst amount 20 mg and initial HCHO concentration 0.16 mg L-.(-1) The enhanced photocatalytic efficiency of K-C3N4/Ag/APM is attributed to the synergistic effect of improved light harvesting, excellent interface contact and accelerated transmission and separation of photogenerated carriers in the Z-scheme structure with Ag as efficient electron transfer mediators. Free radical trapping and electron spin resonance (ESR) experiments confirmed the Z-scheme charge transfer mechanism, and proved that O-center dot(2)- and h(+) were the main active species in HCHO oxidation reaction. The intermediate species in the HCHO photocatalytic degradation process were tested by in situ DRIFTS technology. The construction of g-C3N4 based Z-scheme photocatalyst may provide an insight for the design of new and efficient photocatalysts for environmental applications.

Automated summary

The photocatalytic degradation of formaldehyde is an ideal solution for indoor air pollution. In this study, a ternary heterojunction photocatalyst K-C3N4/Ag/Ag3PMo12O40 was synthesized and it exhibited significantly improved photocatalytic activity compared to other catalysts. The structure and mechanism of the photocatalyst were investigated, providing insights for the design of new and efficient photocatalysts for environmental applications.