Applicability of Nickel-Based Catalytic Systems for Hydrodehalogenation of Recalcitrant Halogenated Aromatic Compounds

This review summarizes recent applications of nickel as a nonprecious metal catalyst in hydrodehalogenation (HDH) reactions of halogenated aromatic compounds (Ar–Xs). Nickel-based HDH catalysts were developed for reductive treatment of both waste containing concentrated Ar–Xs (mainly polychlorinated benzenes) and for wastewater contaminated with Ar–Xs. Ni-catalyzed HDH enables the production of corresponding nonhalogenated aromatic products (Ar–Hs), which are principally further applicable/recyclable and/or Ar–Hs, which are much more biodegradable and can be mineralized during aerobic wastewater treatment. Developed HDH methods enable the utilization of both gaseous hydrogen via the direct HDH process or other chemical reductants as a source of hydrogen utilized in the transfer of the hydrodehalogenation process. This review highlights recent and major developments in Ni-catalyzed hydrodehalogenation topic since 1990.

Theoretical Study on Improving the Catalytic Activity of a Tungsten Carbide Surface for Hydrogen Evolution by Nonmetallic Doping

Tungsten carbide (WC) has received widespread attention as a new type of nonprecious metal catalyst for hydrogen evolution reaction (HER). However, it is still a challenge to improve the surface HER catalytic activity. In this work, the effects of different nonmetallic dopants on the catalytic activity and stabilities of WC (0001) surface for HER were studied by first principles methods. The effects of different types of non-metal (NM = B; N; O; P and S) and doping concentrations (ni = 25–100%) on HER catalytic activity and stability were investigated by calculating the Gibbs free energy of hydrogen adsorption (∆GH) and substitution energy. It was found that the catalytic performance can be improved by doping O and P non-metallic elements. Especially, the ∆GH with P doped is −0.04eV better than Pt (−0.085 eV), which is a potential ideal catalyst for HER. Furthermore, the electronic structure analysis was used to explore the origin of the regulation of doping on stability and catalytic activity. The results show that nonmetallic doping is an effective strategy to control the catalytic activity, which provides theoretical support for the future research of HER catalysts.