Bismuth oxychloride (BiOCl) is a typical UV-light-sensitive photocatalyst with a unique layered structure, but exhibits no response towards visible light. This is a main limitation for its practical applications in photocatalytic degradation of pollutants. Among various methods to expand the light absorption region, doping modification is an efficient approach because it can tailor the band structure by forming a doping energy level without changing the layered structure substantially. In this case, the static electric field in the BiOCl crystal can be retained. Since cobalt (Co) exhibits good electrochemical properties, it is an ideal element for doping modification to expand the light absorption region and enhance the charge separation efficiency of BiOCl. In this work, Co-doped BiOCl nanosheets were prepared using a simple hydrothermal route. The doped Co expanded the light absorption region and enhanced the charge separation efficiency by forming a doping energy level in the band gap of BiOCl. As a result, the Co-BiOCl nanosheets exhibited an outstanding photocatalytic performance in degrading bisphenol A (BPA) under visible light irradiation with a degradation rate of 3.5 times higher than that of BiOCl. On the basis of the experimental results and density functional theory calculations, the mechanism of visible-light-driven catalytic BPA degradation by the Co-BiOCl nanosheets was elucidated. Therefore, the feasibility of Co-doping modification for BiOCl was confirmed, and a novel and efficient strategy was provided for the design and synthesis of high-performance photocatalysts.

Enhanced photocatalytic degradation of bisphenol A by Co-doped BiOCl nanosheets under visible light irradiation

Carbon-doped BiOI (C-BiOI) photocatalysts were successfully synthesized via a hydrothermal method with Bi(NO3)3·5H2O, KI, and glucose as raw materials for the first time. The synthesized samples had excellent photocatalytic activities in the degradation of methyl orange (MO) and the reduction of N2 to NH3. To reveal the origin of the superior photoactivity, the C-BiOI was examined by multi techniques, including N2-adsorption, XRD, SEM, TEM, Raman, XPS, DRS, PL, EIS and transient photocurrent response. The characterization results indicated that the carbon clusters entered the interlayers of BiOI crystal during preparation. The doped carbon interfered the lattice periodicity and generated vacancies in the BiOI structure, resulting in the decreased band gap and increased efficiency in charge separation, both of which could significantly hasten the photocatalytic reaction. Additionally, the introduced carbon affected the morphology of BiOI and increased its specific surface area, which may also benefit the photocatalytic process. The carbon content was crucial to the promotion effect. Under visible light, the optimized carbon-doped BiOI (C-BiOI-2) presented an MO degradation rate of 0.136 min−1, which was 4.44 times higher than that of pure BiOI. However, for the photocatalytic N2 fixation, due to the contribution of surface carbon in N2 adsorption, the C-BiOI sample containing higher carbon content (C-BiOI-3) displayed superior performance than C-BiOI-2. The NH3 generation rate under simulated sunlight reached 311 μmol g−1 h−1, which was about 3.7-fold of that of BiOI. This work may shed some insight into the designing and understanding of carbon-doped semiconductor photocatalysts.

Preparation of interstitial carbon doped BiOI for enhanced performance in photocatalytic nitrogen fixation and methyl orange degradation.

To reduce the recombination of electron-hole pairs, broaden the response scope to visible light, improve the synthesis method and enhance the photocatalytic efficiency of graphite phase carbon nitride (g-C3N4), a novel all-solid direct Z-scheme heterojunction photocatalyst was successfully constructed by in situ growth of bismuth oxyiodide (Bi7O9I3) on ultrathin g-C3N4. The synthesis process was finished under a normal pressure and temperature without any toxic or harmful reagents. As-prepared photocatalyst of BCN-0.2 can be easily excited under visible light and shows an excellent photo-degradation and mineralization capacity of doxycycline hydrochloride. Oxhydryl and superoxide radicals are dominant. Moreover, the Z-scheme heterojunction Bi7O9I3/g-C3N4 has quite stable crystal structure and recycling ability. The present work exhibits a mild and feasible synthesis method for an all-solid direct Z-scheme heterojunction to improve the photocatalytic ability of pollutants.

In-situ growth of all-solid Z-scheme heterojunction photocatalyst of Bi7O9I3/g-C3N4 and high efficient degradation of antibiotic under visible light

Multiply structural optimized strategies for bismuth oxyhalide photocatalysis and their environmental application

Enhanced photocatalytic tetracycline degradation using N-CQDs/OV-BiOBr composites: Unraveling the complementary effects between N-CQDs and oxygen vacancy

Photoinduced oxygen vacancies (OVs) are widely investigated as a vital point defect in wide-band-gap semiconductors. Still, the formation mechanism of OVs remains unclear in various materials. To elucidate the formation mechanism of photoinduced OVs in bismuth oxychloride (BiOCl), we synthesized two surface hydroxyl discrete samples in light of the discovery of the significant variance of hydroxyl groups before and after UV light exposure. It is noted that OVs can be obtained easily after UV light irradiation in the sample with surface hydroxyl groups, while variable changes were observed in samples without surface hydroxyls. Density functional theory (DFT) calculations reveal that the binding energy of Bi–O is drastically influenced by surficial hydroxyl groups, which is intensely correlated to the formation of photoinduced OVs. Moreover, DFT calculations reveal that the adsorbed water molecules are energetically favored to dissociate into separate hydroxyl groups at the OV sites via proton transfer to a...

Hydroxyl-Dependent Evolution of Oxygen Vacancies Enables the Regeneration of BiOCl Photocatalyst

The insufficient light absorption and low quantum efficiency limit the photocatalytic performance of wide bandgap semiconductors. Here, we report a facile strategy to engineer the surface disordered defects of BiOCl nanosheets via carbon doping. The surface defects boost the light absorption and also the quantum yields, as the doped carbon atoms exhibit a transition from sp3 to sp2 hybridization at elevated temperature, corresponding to a change of assembly state from 3D cluster to 2D graphite-like structure. This transition results in an effective charge separation and thus one order of enhancement in photocatalytic activity toward phenol degradation under visible light. The current study opens an avenue to introduce sp3 to sp2 transition of carbon dopants for simultaneous increment of light absorption and quantum efficiency for application in photocatalysis and energy conversion.

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Enhanced photocatalytic activity induced by sp 3 to sp 2 transition of carbon dopants in BiOCl crystals

Facile Mof-on-Mof Isomeric Strategy for Zno@Co3o4 Single-Shelled Hollow Cubes with High Toluene Detection Capability

Au nanoparticles-loaded SnO2 @Fe2O3 multilayer nanosheets (A-SnO2 @Fe2O3 MNSs) with flowerlike appearance and porous feature have been successfully synthesized via a self-template strategy, followed by a Fe2O3-growth and Au-loaded process. The detailed microstructural characterizations confirm that A-SnO2 @Fe2O3 MNSs, besides the loaded Au nanoparticles, are constructed of hetero-alternated Fe2O3/SnO2 sublayers, which are further subdivided into two kinds of primary building blocks, including Fe2O3 nanorods and SnO2 nanoparticles. Benefiting from distinctive structural merits of permeable but interconnected hetero multilayers, A-SnO2 @Fe2O3 MNSs can hold a high surface area and effective gas diffusion during the gas adsorption and desorption process. When used as the sensing materials for acetone detection, A-SnO2 @Fe2O3 MNSs exhibit higher sensitivity and faster response/recovery speed to low-concentration acetone compared with the unloaded components. The promotion of acetone sensing performance is attributed to the dramatic sensitization of the loaded Au nanoparticles. 

Jiawei Xiong

Papers

Hydroxyl-Dependent Evolution of Oxygen Vacancies Enables the Regeneration of BiOCl Photocatalyst

Enhanced photocatalytic activity induced by sp 3 to sp 2 transition of carbon dopants in BiOCl crystals

Facile Mof-on-Mof Isomeric Strategy for Zno@Co3o4 Single-Shelled Hollow Cubes with High Toluene Detection Capability

Novel Au-activated SnO2@Fe2O3 hetero-alternated multilayer nanosheets with enhanced low-concentration acetone detection

Progress of hidden spin polarization in inversion-symmetric crystals