Electrochemical oxidation of water to produce highly reactive hydroxyl radicals (OH) is the dominant factor that accounts for the organic compounds removal efficiency in water treatment. As an emerging carbon-based material, the investigation of electrocatalytic of water to produce OH on Graphdiyne (GDY) anode is firstly evaluated by using first-principles calculations. The theoretical calculation results demonstrated that the GDY anode owns a large oxygen evolution reaction (OER) overpotential (ηOER = 1.95 V) and a weak sorptive ability towards oxygen evolution intermediates (HO*, not OH). The high Gibbs energy change of HO* (3.18 eV) on GDY anode makes the selective production of OH (ΔG = 2.4 eV) thermodynamically favorable. The investigation comprises the understanding of the relationship between OER to electrochemical advanced oxidation process (EAOP), and give a proof-of-concept of finding the novel and robust environmental EAOP anode at quantum chemistry level.@en

Removal of bromate (BrO₃⁻) has gained increasing attention in drinking water treatment process. Photocatalysis technology is an effective strategy for bromate removal. During the photocatalytic reduction of bromate process, the photo-generated electrons are reductive species toward bromate reduction and photo-generated holes responsible for water oxidation. In this study, the monoclinic bismuth vanadate (BiVO₄) single crystal was developed as a visible photocatalyst for the effective removal of bromate. The as-synthesized BiVO₄ photocatalyst with optimized {010} and {110} facets ratio could achieve almost 100% removal efficiency of BrO₃⁻ driven by visible light with a first-order kinetic constant of 0.0368 min⁻¹. As demonstrated by the electron scavenger experiment and density functional theory (DFT) calculations, the exposed facets of BiVO₄ should account for the high photocatalytic reduction efficiency. Under visible light illumination, the photo-generated electron and holes were spatially transferred to {010} facets and {110} facets, respectively. The BiVO₄ single crystal photocatalyst may serve as an attractive photocatalyst by virtue of its response to the visible light, spatially charge transfer and separation as well as high photocatalytic activity, which will make the removal of BrO₃⁻ in water much easier, more economical and more sustainable.

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2D-g-C₃N₄ nanosheet was prepared and employed for the adsorption of elemental mercury (Hg⁰). The g-C₃N₄ was analyzed through X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) methods, and the results showed that the prepared sample was well-defined 2D-nanosheet. The 2D-g-C₃N₄ sorbent exhibited a high Hg⁰ removal efficiency (> 90%) at the condition of temperature 120 °C. To investigate the mechanism of Hg⁰ adsorption on the 2D-g-C₃N₄ surface, corresponding theoretical exploration based on the first principle prediction and X-ray photoelectron spectroscopy (XPS) test was implemented. The DFT calculation results showed that Hg⁰ was strongly bound to the B₁ site of the g-C₃N₄ surface with an adsorption energy change of -162.2 kJ mol⁻¹, the equilibrium distance of Hg-C was 3.473 Å, and electron transfer between Hg and C atoms was 0.02. The results of XPS showed the main species of mercury was HgO on the surface of 2D-g-C₃N₄ sample and the interaction between C₃N₄ surface and Hg⁰ was physisorption. This study provides a demonstration of proof-of-concept demonstration that g-C₃N₄ is a promising sorbent capable of capturing Hg⁰, and presents in-depth understanding of Hg⁰ adsorption mechanism on 2D-g-C₃N₄ sorbent.

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