Construction and mechanistic insights of 2D/2D Z-scheme Bi<inf>3</inf>TiNbO<inf>9</inf>/BiOBr heterojunction for enhanced photocatalytic organic pollutant removal

Abstract

Bismuth-based layered ferroelectrics are believed to be promising photocatalysts, but the limited visible-light harvesting and severe charge carrier recombination are still restricting the overall photocatalytic efficiency. Herein, a novel 2D/2D Z-scheme Bi3TiNbO9/BiOBr heterojunction was constructed combining molten salt and hydrothermal synthesis methods. An intimate conjunction between Bi3TiNbO9 and BiOBr nanosheets was confirmed which inhibited charge carrier recombination and promoted carrier mobility in the nanocomposites. Benefiting from the optimized charge carrier kinetics and the broadened spectral response range compared to Bi3TiNbO9, the photodegradation rate of tetracycline hydrochloride by Bi3TiNbO9/3BiOBr reached 0.0228 min−1, which was 6.5 and 1.5 times that of Bi3TiNbO9 and BiOBr, respectively. Furthermore, the heterojunction has also shown satisfactory recycling stability and degradation universality for common organic pollutions including dyes and antibiotics. According to the density functional theory (DFT) calculations and experimental analysis of active species, a 2D/2D Z-scheme Bi3TiNbO9/BiOBr heterostructure was demonstrated and the possible working mechanisms were discussed. This work is hoped to add another layer of understanding depth to the design and fabrication of 2D/2D Z-scheme heterojunctions of bismuth-based layered ferroelectric photocatalysts.