Development and study of a bifunctional photocatalyst based on SAPO-34 molecular sieve

Abstract

A new bifunctional photocatalyst was constructed from a modified SAPO-34 molecular sieve successfully connected with BiVO₄ crystals through O bridges. The new as-fabricated catalyst not only had enriched active sites of B-acid and L-acid on the surface of the molecular sieve but also enriched active sites of L-acid on the surface of the molecular sieve. The electron-transfer ability between the SAPO-34 molecular sieve and BiVO₄ crystals was improved, and the recombination of electrons and holes in BiVO₄ crystals was inhibited. With the synergistic action of the B-acid and L-acid, the molecular zeolite showed very high activity for the photocatalytic degradation of formaldehyde aqueous solution with a photoreaction rate constant of 0.291 min⁻¹ and degradation rate of 84.34%. Compared with the BiVO₄ crystal, the performance improved 10 times. Based on the calculation of the band structure and state density of the BiVO₄ crystal and the HOMO and LUMO energy levels of the SAPO-34 molecular sieve, a mechanism for the photocatalytic degradation of formaldehyde is proposed and the energy levels of the intermediate products were calculated. This study provides a method for the preparation of composite molecular sieve photocatalysts and a new idea for the construction of bifunctional photocatalysts.