Fabrication of BiOCl with adjustable oxygen vacancies and greatly elevated photocatalytic activity by using bamboo fiber surface embellishment

Highlights

• Bamboo fiber (BF) was utilized to modify BiOCl.

• Modification of BiOCl by BF can adjust the concentration of OVs.

• Modification of BiOCl by BF promote the separation of carriers.

• BiOCl modified by BF possesses prominent photocatalytic activity.

Abstract

In this demonstration, to promote the photocatalytic activity of BiOCl, environmentally friendly bamboo fiber (BF) was added into the synthesis system of BiOCl. The size of crystals and the content of oxygen vacancies (OVs) can be effectively controlled by BF. The crystal structure, morphology, light absorbance capacity, separation efficiency of photogenerated carriers, OVs, microchemical environment, active free radicals and photocatalytic performance were carefully investigated. The observations firmly confirm that BF can effectively affect the growth of BiOCl. More interestingly, the content of OVs can be easily regulated by adjusting the amount of BF. When the mass ratio of BF/BiOCl is 0.5%, the composite has the richest OVs and the best photocatalytic activity. Compared with the reference BiOCl, the degradation efficiency of tetracycline (TC) and Rhodamine B (RhB) on 0.50% BF-BOC under visible light irradiation increases by 7.2 times and 4.1 times, respectively. Moreover, the sample holds high defluorination efficiency toward destruction of perfluorooctanoic acid (PFOA) than the reference BiOCl, which can be allocated to the greatly enhanced separation efficiency of photogenerated carriers and abundant OVs. This work provides an alternative strategy for preparation of highly activity photocatalysts for water pollution treatment.

Introduction

Recently, the issue of water pollution caused by organic hazards has received extensive attention. Organic pollutants such as dyes [1], [2], antibiotics [3], [4], [5] and persistent organic pollutants (POPs) [6], [7], [8] are ubiquitous in the environment due to their wide application, causing a serious threat to the natural environment and human health. Therefore, how to deal with these organic pollutants has become a hot spot for scientists. Various strategies have been developed to eliminate environmental pollution [9], [10], [11]. Amongst the approaches developed, semiconductor photocatalytic technology is deemed as one of the most prospective technologies to relieve environmental pollution [12], [13], [14], [15]. Development of photocatalysts with high photocatalytic activity is the core of photocatalysis. BiOCl with a layered crystal structure has been proven to a promising photocatalyst, and some studies support that BiOCl exhibits higher photoactivity than TiO₂ [16]. However, the separation efficiency of e^--h⁺ pairs is still not ideal for practical application [17], [18]. Hence, how to ameliorate the separation of electron and hole pairs (e^--h⁺) is the core issue. In order to solve this problem, researchers have developed several strategies, such as element doping [19], [20], [21], morphology modification [22], [23], introduction of OVs [24], [25] and construction of heterojunctions [26], [27], [28].

Introduction of OVs is considered to be an effective approach to boost the performance of photocatalysts [29], [30], [31]. OVs can capture electrons, thus improving the separation efficiency of photogenerated e^--h⁺ pairs [32], [33]. OVs will build a new energy level between valence band (VB) and conduction band (CB) [34], [35], [36], [37], which will narrow the energy band width of the semiconductor, thereby broadening the light absorption capacity [36], [37]. Moreover, OVs can provide additional active sites to adsorb O₂ to form superoxide radicals (•O₂^-) [38], improving photocatalytic performance of the photocatalyst. Nowadays, some special approaches are employed to produce oxygen deficiency in the crystal lattice of the oxygen-containing metal compound, such as high-temperature calcination [39], radio frequency sputtering [40] and surface etching [41]. Although these methods can availably introduce OVs, they have high energy consumption, cumbersome steps, or high equipment costs, therefore, it is absolutely essential to establish a green and facile approach to introduce OVs.

Morphology modification is an available method to ameliorate the activity of photocatalyst by controlling the morphology of the photocatalyst and regulating OVs. Some templates have been reported to be used as substrates to regulate the growth of photocatalysts, altering the original morphology and introducing abundant OVs, thereby boosting the active of photocatalysts [42], [43], [44].

BF not only has cracks on the surface, but also has a natural porous and hollow structure. Therefore, in this demonstration, BF was used to modify BiOCl to fabricate photocatalysts with greatly boosted photocatalytic performance. In order to evaluate the photocatalyst removal of the aforementioned three typical organic pollution, RhB, TC and PFOA were selected as simulated pollutants, and the decontamination ability of BF-BiOCl has been greatly improved. Given the characterization results, it can be found that the separation efficiency of photoinduced charge of BiOCl modified by BF is significantly improved, and the amount of OVs can be easily adjusted. The increase of OVs and the enhancement of e^--h⁺ separation efficiency jointly promote the photocatalytic performance of BiOCl.