Even though the well-established Haber-Bosch process has been the major artificial way to "fertilize" the earth, its energy-intensive nature has been motivating people to learn from nitrogenase, which can fix atmospheric N2 to NH3 in vivo under mild conditions with its precisely arranged proteins. Here we demonstrate that efficient fixation of N2 to NH3 can proceed under room temperature and atmospheric pressure in water using visible light illuminated BiOBr nanosheets of oxygen vacancies in the absence of any organic scavengers and precious-metal cocatalysts. The designed catalytic oxygen vacancies of BiOBr nanosheets on the exposed {001} facets, with the availability of localized electrons for π-back-donation, have the ability to activate the adsorbed N2, which can thus be efficiently reduced to NH3 by the interfacial electrons transferred from the excited BiOBr nanosheets. This study might open up a new vista to fix atmospheric N2 to NH3 through the less energy-demanding photochemical process.

A general one-pot solvothermal process was explored to prepare BiOX (X = Cl, Br, I) powders by employing ethylene glycol as the solvent. The as-prepared BiOX powders were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV−vis diffuse reflectance spectroscopy, and nitrogen sorption. The resulting BiOX samples were phase-pure and of hierarchical microspheres consisting of nanoplates. The band gaps of the as-prepared powders were estimated to about 3.22, 2.64, and 1.77 eV for BiOCl, BiOBr, and BiOI, respectively. On the basis of characterization results, we proposed a possible process for the growth of hierarchical BiOX nanoplate microspheres. Moreover, we evaluated their photocatalytic activities on the degradation of methyl orange and compared them with TiO2 (Degussa, P25) under UV−vis light irradiation and C-doped TiO2 under visible light (λ > 420 nm) irradiation, respectively. It was found that all the BiOX samples were photocatalytically active and BiOI exhibited excellent activity under both UV−vis and visible light irradiation. The resulting hierarchical BiOX nanoplate microspheres are very promising photocatalysts for degrading organic pollutants and other applications.

Semiconductor photocatalysis is a trustworthy approach to harvest clean solar light for energy conversions, while state-of-the-art catalytic efficiencies are unsatisfactory because of the finite light response and/or recombination of robust charge carriers. Along with the development of modern material characterization techniques and electronic-structure computations, oxygen vacancies (OVs) on the surface of real photocatalysts, even in infinitesimal concentration, are found to play a more decisive role in determining the kinetics, energetics, and mechanisms of photocatalytic reactions. This Review endeavors to clarify the inherent functionality of OVs in photocatalysis at the surface molecular level using 2D BiOCl as the platform. Structure sensitivity of OVs on reactivity and selectivity of photocatalytic reactions is intensely discussed via confining OVs onto prototypical BiOCl surfaces of different structures. The critical understanding of OVs chemistry can help consolidate and advance the fundamental theories of photocatalysis, and also offer new perspectives and guidelines for the rational design of catalysts with satisfactory performance.

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In this study, hierarchical bismuth oxybromide (BiOBr) nanoplate microspheres were used to remove NO in indoor air under visible light irradiation. The BiOBr microspheres were synthesized with a nonaqueous sol-gel method by using bismuth nitrate and cetyltrimethyl ammonium bromide as the precursors. On degradation of NO under visible light irradiation (lambda > 420 nm) at 400 part-per-billion level, which is typical concentration for indoor air quality, these nonaqueous sol-gel synthesized hierarchical BiOBr microspheres exhibited superior photocatalytic activity to the chemical precipitation synthesized counterpart BiOBr bulk powder and Degussa TiO2 P25 as well as C doped TiO2. The excellent catalytic activity and the long-term activity of nonaqueous sol-gel synthesized BiOBr microspheres were attributed to their special hierarchical structure, which was favorable for the diffusion of intermediates and final products of NO oxidation. Ion chromatograph results confirmed that nitric acid was produced on the surface of BiOBr microspheres during the photooxidation of NO in gas phase. This work suggests that the nonaqueous sol-gel synthesized BiOBr nanoplate microspheres are promising photocatalytic materials for indoor air purification.