Engineering direct Z-scheme GCN/ bimetallic-MOF heterojunctions as efficient and recyclable photocatalysts for enhancing degradation of RR 195 under visible light

Abstract

Direct Z-scheme heterojunction photocatalyst GCN/M-FeBTC (M: Ni, Co, Cu, Zn, Mn; BTC: 1,3,5-benzenetricarboxylate, GCN: graphitic carbon nitrides) were synthesized by in-situ hydrothermal method assisted using microwave. GCN/M-FeBTC materials exhibit excellent photocatalytic performance with nearly 100 % of reactive red 195 (RR-195) being removed after 30 min under direct sunlight irradiation. Tests for reactive radicals have shown that holes (h+) and superoxide radicals (•O2–) close a major function in the removal of RR-195. Based on the band structure (BS) of the material, a direct Z-scheme heterojunction photocatalyst mechanism has been proposed. The effects of catalyst mass, pH and RY-145 concentration on the photocatalytic activity of GCN/Mn-FeBTC materials were also researched. The innovation of the photocatalytic activity of the GCN/Mn-FeBTC materials may be due to the synergistic combination of factors such as: (i) the high surface area; (ii) visible light absorption and efficient splitting of electron (e–) and h+; (iii) increased oxygen vacancies and defects; (iv) shortening of charge transport distances. The decomposition pathway of RR-195 was determined based on liquid chromatography mass spectrometry (LC-MS) analysis. Chemical oxygen demand (COD), biological oxygen demand (BOD) and total organic carbon (TOC) show high mineralization potential for the degradation of RR-195 on direct Z-scheme photocatalysts GCN/M-FeBTC.