Enhancement of photocatalytic bromate reduction by TiO2 coupled with Ti3C2MXene as efficient non-noble cocatalyst: Performance and mechanism

Although considered as a promising candidate for photocatalytic bromate reduction, TiO 2 is restricted by its fast recombination of photo-induced charge carriers. In this paper, a series of efficient photocatalysts (TiO 2 /TC) were prepared by coupling commercial titania (P25) with titanium carbide MXene (Ti 3 C 2 ) via a simple hydrothermal method, where Ti 3 C 2 was utilized as a noble-metal-free cocatalyst. Batch experiments of photocatalytic bromate removal by TiO 2 /TC composites were conducted under UV irradiation. Its performance and mechanism were also investigated. The results showed that more than 95% of bromate could be removed by TiO 2 /TC-1 composite (Ti 3 C 2 and P25 in a mass ratio of 1%) in 15 min, and its removal rate was 4.87 times higher than that of pure P25. The photocatalytic reduction of bromate by TiO 2 /TC was an interfacial reaction, and bromide was the main product. The greatly improved activity of TiO 2 /TC composites was attributed to the improved separation efficiency of photogenerated charge carriers and narrower band gap. TiO 2 /TC-1 composite exhibited a longer lifetime (6.05 ns) of electron-hole pairs than pristine P25 (4.31 ns). Moreover, due to its excellent electrical conductivity, Ti 3 C 2 functioned as “an electron sink” to accumulate photoinduced electrons from the excited P25. And the Schottky barrier formed in the tight Ti 3 C 2 -P25 interface provided a unidirectional channel for electron transfer , facilitating the separation of electron-hole pairs. In addition, TiO 2 /TC-1 composite had a good stability in bromate removal. This work highlights the potential of Ti 3 C 2 as a noble-metal-free photocatalytic cocatalyst and explores the possible expansion of the application of MXene.