Construction and in-situ thermodynamics/kinetics studies on Ag-bridged g-C3N4-{002}/BiOBr-{001} facet Z–scheme heterojunction with crystal plane synergistic effect based on photocalorimetry - spectroscopy technology

In this study, a novel Ag-bridged g-C3N4-{002}/BiOBr-{001} facet Z-scheme heterojunction nanocomposites with synergistic effect of crystal plane had been created, and its photocatalytic degradation performance for Rhodamine 6G (Rh-6G) had been evaluated. The resulting g-C3N4@Ag@BiOBr not only followed the Z-scheme interface transfer mechanism, but also showed good synergy between the highly exposed g-C3N4-{002} and BiOBr-{001} crystal planes, exhibiting better Rh-6G degradation performance, compared with the two-component g-C3N4@Ag and g-C3N4@BiOBr heterojunction systems. Photocalorimetry-spectroscopic study on the thermodynamics/kinetics mechanism of g-C3N4@Ag@BiOBr photocatalytic degradation of Rh-6G helped to unlock the degradation mechanism. Three main heat exchanges were detected during the photocatalytic action, corresponding to the electron-hole pair generation, Rh-6G degradation by active species, and the final stable exothermic stage with a stable exothermic rate of (-0.4592 +/- 0.2368) mJ.s(-1). The whole process corresponded to that N-de-ethylated, deaminization and other cleavage of the fluorescent chromophore reaction for Rh-6G occurred rapidly within 30 min, then the mineralization and degradation of non-fluorescent chromophore intermediates which were the rate-determining steps eventually dominated, in accordance with the final stable exothermic stage of a pseudo-zero-order process. The results demonstrated that the photocatalytic degradation of Rh-6G over g-C3N4@Ag@BiOBr was a pseudo-zero-order reaction rather than a firstorder reaction as measured by universal spectroscopic method. This study not only created highly efficient composites photocatalysts, but also shed new light on revealing the photocatalytic mechanism using the complete expression of thermodynamics, kinetics and spectral kinetics. (C) 2022 Elsevier Inc. All rights reserved.