Herein, mesoporous NiFe2O4 spinel nanoparticles with abundant oxygen vacancies are successfully prepared by a simple hydrothermal method followed by mild H2 reduction and used as catalysts for the oxygen evolution reaction. Compared with the pristine and air‐treated NiFe2O4, the H2‐treated NiFe2O4 shows a much lower overpotential of 389 mV at a current density of 10 mA cm−2. The H2‐treated NiFe2O4 also indicates substantial long‐term stability even after 1000 cyclic tests. This outstanding electrochemical activity and stability can be attributed to the improved physicochemical properties by H2 treatment: small nanoparticles with well‐developed mesoporous structures, a high ratio of Ni2+/Ni3+ cations, and abundant oxygen vacancies. These properties can significantly improve charge transfer kinetics and increase the number of active sites on the catalyst. The results demonstrate that this facile fabrication method is a promising route for developing cost‐effective and high‐performance catalysts to be used in electrochemical applications.

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We propose a simple method to investigate both the qualitative and quantitative properties of titanium tetrachloride. The selection and concentration of the employed solvent were found to be very important in the analysis of highly reactive titanium tetrachloride (TiCl4). Herein, we employed various concentrations of an acid solution to serve as a stabilizing medium. Qualitative analysis was performed via Fourier transform-infrared spectroscopy (FT-IR) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). Additionally, the quantitative analysis was performed via inductively coupled plasma optical emission spectroscopy (ICP-OES). We concluded that both the qualitative and quantitative properties of titanium tetrachloride could be easily measured using a specific acidic solvent as a medium.

Spinel‐type NiFe2O4 with oxygen vacancies was prepared via a simple hydrothermal method followed by mild reduction under hydrogen flow and used as a catalyst for the oxygen evolution reaction (OER). The oxygen‐deficient spinel‐type oxide nanoparticles exhibited excellent electrocatalytic activity and long‐term durability for the OER in alkaline medium. The outstanding electrochemical performance was attributed to the improved physicochemical properties by induced oxygen vacancies. More information can be found in the Full Paper by Sung‐Hyeon Baeck et al. on page 1296 in Issue 10, 2019 (DOI: 10.1002/cnma.201900231).