Wong, Kien Tiek Kim, Seung Chul Yun, Kayoung Choong, Choe Earn Nah, In Wook Jeon, Byong-Hun Yoon, Yeomin Jang, Min 2024-01-19T16:33:25Z 2024-01-19T16:33:25Z 2021-09-02 2020-09-15 0926-3373 https://pubs.kist.re.kr/handle/201004/118118 A new approach to determine the importance of band potential by comparing two different electron charge transfer mechanism, via Z-scheme and type-II heterojunction. Through microwave hydrothermal (MWH) treatment and subsequent thermal polycondensation, the released ammonia gas from the formation of oxidized GCN simultaneously reducing the surface of TiO2 (designated as mwh-CNTO), hence creating a sub-gap state between the interface of these two catalysts. Compared to pristine photocatalysts, mwh-CNTO-0.1 (0.1 g TiO2 with 6 g melamine) has shown superior photocatalytic activities (between 6 to 34-folds) under monochromatic LED (400 nm) and natural sunlight. Since TiO2 in the composite cannot be activated under LED, the bands alignment from type-II heterojunction decreases the overall band potential, resulting in mainly center dot O-2(-) (anionic) generated. Consequently, non-charged BPA was effectively degraded with a kinetic rate constant of 0.0310 min(-1), while negatively charged ATZ had much lower rate constant (0.0043 min(-1)) due to their repulsive properties. In contrast, natural sunlight (full spectrum) could not only activate both TiO2 and GCN of mwh-CNTO-0.1, but also induce Z-scheme mechanism via driving the photogenerated electrons (TiO2) through the created sub-gap state and ultimately recombining at valence band (VB) of GCN. As proven by detection of DMPO-center dot OH, scavenging tests and DFT modeling, this scheme effectively degraded both BPA (0.0379 min(-1)) and ATZ (0.0474 min(-1)) owing to the VB position of TiO2 being maintained to generate non-selective center dot OH. Overall, in comparison to other studies, the proposed Z-scheme on mwh-CNTO-0.1 had much higher energy efficiencies for BPA (8.2 x 10(-3) min(-1) W-1) and ATZ removal (1.0 x 10(-2) min(-1) W-1) under natural sunlight. English ELSEVIER HIGH-SURFACE-AREA VISIBLE-LIGHT PHOTOCATALYTIC ACTIVITY G-C3N4 NANOSHEETS CARBON NITRIDE DOPED G-C3N4 QUANTUM DOTS ULTRATHIN G-C3N4 CYANURIC ACID TIO2 Understanding the potential band position and e-/h(+) separation lifetime for Z-scheme and type-II heterojunction mechanisms for effective micropollutant mineralization: Comparative experimental and DFT studies Article 10.1016/j.apcatb.2020.119034 1 APPLIED CATALYSIS B-ENVIRONMENTAL, v.273 APPLIED CATALYSIS B-ENVIRONMENTAL 273 scie scopus 000536933200011 2-s2.0-85084483936 Chemistry, Physical Engineering, Environmental Engineering, Chemical Chemistry Engineering Article HIGH-SURFACE-AREA VISIBLE-LIGHT PHOTOCATALYTIC ACTIVITY G-C3N4 NANOSHEETS CARBON NITRIDE DOPED G-C3N4 QUANTUM DOTS ULTRATHIN G-C3N4 CYANURIC ACID TIO2 Photocatalysis Organic pollutants Z-scheme Sunlight Microwave hydrothermal Treatment