Construction of ß-Bi2O3/Bi2O2CO3 heterojunction photocatalyst for deep understanding the importance of separation efficiency and valence band position.

Constructing heterojunctions would result in the change of valence band position, which is an important factor determining the oxidative ability of photo-induced holes, has received scant attention. In this paper, ß-Bi2O3/Bi2O2CO3 composites with different ratios were obtained via ionic-liquid-assisted solvothermal and in-situ calcination processes. UV-vis DRS, Mott-Schottky test, and Kelvin probe measurement showed the change of band gaps of ß-Bi2O3 and Bi2O2CO3 before and after heterojunction formation. SPV, ESR, photocurrent, and scavenger experiments identified the separation efficiency of photo-generated electrons and holes, as well as the active species generated in the photocatalytic process. The photocatalytic mechanism was investigated by the degradation of Rhodamine B (RhB) upon visible-light and simulated sunlight, respectively. The results demonstrated that ß-Bi2O3/Bi2O2CO3 heterojunctions possessed enhanced separation efficiency and higher degradation ability than the individuals under visible-light irradiation due to effective electron transfer. However, lower performance under simulated sunlight was observed, although their separation efficiency remained high. The decisive reason for this was that the up-shift of valence band of Bi2O2CO3 induced by hybridization and the transition of holes from VB of Bi2O2CO3 to that of ß-Bi2O3 with more negative potential decreased the oxidative ability of holes, which surpassed the positive influence of enhanced separation efficiency.

[Practical exploration on the Online Four-step Teaching of Encouraging and Sharing during COVID-19 period].

The "Four-step Teaching of Encouraging and Sharing" is a learner-centered teaching method that advocates teamwork and gives full play to the role of the teacher in guiding learning. It is an innovative teaching approach to realize students' self-transcendence by stimulating students' internal motivation for independent learning, applying group task-driven learning, and giving teachers' feedback to students' sharing. It consists of four steps: teachers' guiding, students' self-regulated learning, team learning and practice, experience sharing. We have applied this method to the teaching practice of physiology and experimental physiological science with a significant impact on teaching effects. This teaching method has also been implemented to other courses in other majors. To solve the problems of reduced communication and interaction, low learning enthusiasm and motivation in online teaching course during COVID-19 pandemic, we recruited 21 undergraduates from different schools and majors. Using the "Tencent Meeting" platform, the authors tried to apply the whole process of the "Four-step Teaching of Encouraging and Sharing" to the online teaching of physiology. Group tests and questionnaires were used to evaluate teaching effects. The results showed that the implementation of the "Online Four-step Teaching of Encouraging and Sharing (OFST)" was feasible and effective, and to a certain extent alleviated the problems of loneliness and low learning motivation of students during online learning caused by home quarantine, which was particularly helpful for long-distance inter-school and inter-discipline team learning.