Bismuth-doped ZIF-8 as a highly efficient piezo-photocatalyst for advanced remediation of organic dyes
摘要
The synergy between photocatalytic and piezoelectric processes is considered a promising new approach for degrading complex organic contaminants. This research focuses on a hybrid technique that integrates these two effects using metal-organic frameworks doped with multi-metal ions. Thus, several piezo-photocatalysts with varying weight percentages of bismuth-doped ZIF-8 (wt%-BDZ) were synthesized via in situ fabrication and used for the degradation of acid black-2 (Nigrosine, NG) dye. The constructed catalysts were characterized using various techniques, including FT-IR, FESEM/EDX, LSV, XRD, UV-DRS, EIS, PL, TEM, and BET analysis, which confirmed the effective incorporation of bismuth into ZIF-8. Noticeably, the 10 wt% Bi-doped ZIF-8 (10%-BDZ) sample exhibited the best piezo-photocatalytic performance (reaching 88.92% within 120 min) compared with both photo- and piezo-catalytic processes under sonic vibration and visible light irradiation, representing a 1.8-fold improvement over pristine ZIF-8. The 10%-BDZ followed a pseudo-first-order model with a degradation rate constant of k = 0.027 min− 1. Moreover, after four cycles of piezo-photocatalytic reactions, the 10%-BDZ exhibited noteworthy stability. The holes (h+) and superoxide radical (•O2_) were the crucial reactive species involved in the piezo-photodegradation process. The results indicated that adding Bi to ZIF-8 enhanced the degradation efficiency due to Bi-induced defect states, which act as photogenerated electron trapping centres. Furthermore, it introduced a piezoelectric effect that greatly facilitated the separation of photocharge carriers via electrical polarization.