ABSTRACT
In recent years, it has been found that adjusting the organizational structure of Co3O4 through solid solution and other methods can effectively improve its catalytic performance for the oxidation of low concentration methane. Its catalytic activity is close to that of metal Pd, which is expected to replace costly noble metal catalysts. Therefore, the in-depth research on the mechanism and methods of Co3O4 microstructure regulation has very important academic value and economic benefits. In this paper, we reviewed the catalytic oxidation mechanism, microstructure regulation mechanism, and methods of nano-Co3O4 on methane gas, which provides reference for the development of high-activity Co3O4-based methane combustion catalysts. Through literature investigation, it is found that the surface energy state of nano-Co3O4 can be adjusted by loading of noble metals, resulting in the reduction of Co-O bond strength, thus accelerating the formation of reactive oxygen species chemical bonds, and improving its catalytic effect. Secondly, the use of metal oxides and non-metallic oxide carriers helps to disperse and stabilize cobalt ions, improve the structural elasticity of Co3O4, and ultimately improve its catalytic performance. In addition, the performance of the catalyst can be improved by adjusting the microstructure of the composite catalyst and optimizing the preparation process. In this review, we summarize the catalytic mechanism and microstructure regulation of nano-Co3O4 and its composite catalysts (embedded with noble metals or combined with metallic and nonmetallic oxides) for methane combustion. Notably, this review delves into the substance of measures that can be used to improve the catalytic performance of Co3O4, highlighting the constructive role of components in composite catalysts that can improve the catalytic capacity of Co3O4. Firstly, the research status of Co3O4 composite catalyst is reviewed in this paper. It is hoped that relevant researchers can get inspiration from this paper and develop high-activity Co3O4-based methane combustion catalyst.
ABSTRACT
Most sheet facial masks for skincare are made of nonwovens and loaded with liquid active ingredients, which are usually opaque and require additives for long-term preservation. Herein, a Transparent Additive-Free Fibrous (TAFF) facial mask is reported for skin moisturizing. The TAFF facial mask consists of a bilayer fibrous membrane. The inner layer is fabricated by electrospinning functional components of gelatin (GE) and hyaluronic acid (HA) into a solid fibrous membrane to get rid of additives, the outer layer is an ultrathin PA6 fibrous membrane that is highly transparent, especially after absorbing water. The results indicate that the GE-HA membrane can quickly absorb water and become a transparent hydrogel film. By employing the hydrophobic PA6 membrane as the outer layer, directional water transport is achieved, which enables TAFF facial mask with excellent skin moisturizing effect. The skin moisture content is up to 84% ± 7% after placing the TAFF facial mask on the skin for 10 min. In addition, the relative transparency of the TAFF facial mask on the skin reaches 97.0% ± 1.9% when ultrathin PA6 membrane is used as the outer layer. The design of the transparent additive-free facial mask may serve as a guideline for developing new functional facial masks.
