Hydrothermal construction of flower-like g-C3N4/NiZnAl-LDH S-scheme heterojunction with oxygen vacancies for enhanced visible-light triggered photocatalytic performance

Abstract

Construction of S-scheme heterojunction with high photocatalytic performance has been regarded as a promising way to treat organic wastewater thoroughly. In the present work, a novel S-scheme heterojunction with oxygen vacancies was successfully constructed between graphitic-carbon nitride(g-C3N4) nanosheets and NiZnAl layered double hydroxide (NiZnAl-LDH) by hydrothermal method. The as-synthesized g-C3N4/NiZnAl-LDH heterojunction displayed superior photocatalytic degradation activity over methyl orange (MO) and tetracycline (TC) aqueous solution compared with the pristine g-C3N4 and NiZnAl-LDH. Dramatically, the sample g-C3N4/NiZnAl-LDH (23%) exhibited the best photocatalytic activity, the photodegradation rate constants are 3.5, 12.7 times and 3.2, 5.5 times to pristine g-C3N4 and NiZnAl-LDH, respectively for the degradation of MO and TC. The enhanced photocatalytic activity is mainly due to the formation of S-scheme heterojunction modified by oxygen vacancy. In addition, a reasonable photocatalytic mechanism was proposed based on the photoluminescence (PL), electrochemical impedance (EIS), transient photocurrent test, active species capture and electron spin response (ESR/EPR) experiments combined with high performance liquid chromatography-mass spectrometry (HPLC-MAS) and total organic carbon (TOC) analysis. This work affords a new approach for the construction of efficient, stable and potential applications of g-C3N4 based S-scheme heterojunction photocatalysts.