ZIF-8 derived carbon/g-C3N4-an all-carbon heterojunction for effective photo-decontamination of Cr(VI) from water

Carbon-based heterojunctions, because of their low toxicity and non-polluting properties, are considered as metal-free alternatives to the traditional metal oxide semiconductors for energy and environmental ap-plications especially in acidic conditions. In this work, an all-carbon heterojunction using exfoliated gra-phitic carbon nitride (GCN) and porous carbon derived from zeolitic imidazolate framework (CZ8) is developed for chromium (VI) decontamination. The enhanced charge-transfer in the GCN:CZ8 hetero-junctions, due to the suppressed electron-hole pair recombination, is evidenced from photoluminescence (PL) spectroscopy, transient photocurrent (TP) measurements and electrochemical impedance spectroscopy (EIS). This phenomenon significantly contributes towards improving the photo-induced decontamination of the noxious Cr(VI). Moreover, the band gap of the optimized GCN:CZ8 heterojunction is 2.48 eV which is relatively narrow than that of the GCN (2.79 eV). Nearly 100 % removal is achieved with the as-synthesized GCN:CZ8 heterojunction even with chromium solution of 100 ppm concentration. The X-Ray photoelectron spectroscopy (XPS) results suggest the facile reduction of Cr(VI) to Cr(III) under the influence of incident photons, and most importantly, the performance efficiency of the heterojunction is maintained similar to 100 % up to five continuous cycles. Herein, the optimized GCN:CZ8 heterojunction is established as a potential ma-terial towards efficient decontamination of Cr(VI) from water.(c) 2023 Elsevier B.V. All rights reserved.