G-C3N4 doping TiO2 recovered from spent catalyst for H2 evolution from water

Abstract

Spent catalysts of selective catalytic reduction (SCR) contain a high content of TiO2 (>70 wt%). The effective recovery of TiO2 from spent SCR catalysts and its reuse in photocatalytic hydrogen production is of great importance for environmental protection. In this study, the recovered TiO2 from the spent SCR catalyst was recovered by the alkali washing method, and the purity of the recovered TiO2 reached 94.7%. g-C3N4 as a co-catalyst and enhanced the separation efficiency of the photogenerated electron-hole pairs of the TiO2 photocatalyst. The composite photocatalyst R–TiO2/g-C3N4 prepared by directly mixing the recovered TiO2 with g-C3N4 significantly improved the photocatalytic activity. The experimental design of the photocatalyst synthesis was optimized using the Design Expert software. The results showed that the recovered TiO2 was 0.334 g when the g-C3N4 was 0.046 g and the ultrasonic time was 163 min. Moreover, the hydrogen production rate reached 443.105 μmol g−1 h−1 within 4 h.