A mass-producible integrative structure Pt alloy oxygen reduction catalyst synthesized with atomically dispersive metal-organic framework precursors

A review of ordered PtCo3 catalyst with higher oxygen reduction reaction activity in proton exchange membrane fuel cells

This review is devoted to the potential advantages of ordered alloy catalysts in proton exchange membrane fuel cells (PEMFCs), specifically focusing on the development of the low Pt content, high activity, and durability ordered PtCo3 catalyst. Due to the sluggish oxygen reduction reaction (ORR) kinetics and poor durability, the overall performance of the fuel cell is affected, and its application and promotion are limited. To address this issue, researchers have explored various synthetic strategies, such as element doping, morphology adjusting, structure controlling, ordering and support/metal interaction enhancement. This article extensively discussed the Pt related ORR catalysts and follows an in-depth analysis of ordered PtCo3. The introduction briefly discusses the direction of development of fuel cell catalysts and frontier progress, including theoretical mechanism, practical preparation, and Pt-containing electrode structures, etc. The subsequent chapter focuses on the Pt-Co catalyst, the evolution process of Pt alloy to Pt-Co alloy and the improvement scheme are introduced. The next chapter describes the properties of PtCo3. Although the ordered PtCo3 catalyst has a wide range of applicability due to low cost and high activity catalyst. However, besides the common agglomeration and sintering problems of Pt-Co alloy, its commercial application still faces unique problems of oversized crystal size, phase segregation, ordering transformation and transition metal dissolution. Therefore, in Chapter 4, this overview provides some possible improvement methods for three specific functions: crystal refinement, enhancing the effect of support and active substances, and anti-dissolution.

Systematic Study of Effective Hydrothermal Synthesis to Fabricate Nb-Incorporated TiO2 for Oxygen Reduction Reaction

Fuel cells are expected to serve as next-generation energy conversion devices owing to their high energy density, high power, and long life performance. The oxygen reduction reaction (ORR) is important for determining the performance of fuel cells; therefore, using catalysts to promote the ORR is essential for realizing the practical applications of fuel cells. Herein, we propose Nb-incorporated TiO₂ as a suitable alternative to conventional Pt-based catalysts, because Nb doping has been reported to improve the conductivity and electron transfer number of TiO₂. In addition, Nb-incorporated TiO₂ can induce the electrocatalytic activity for the ORR. In this paper, we report the synthesis method for Nb-incorporated TiO₂ through a hydrothermal process with and without additional load pressures. The electrocatalytic activity of the synthesized samples for the ORR was also demonstrated. In this process, the samples obtained under various load pressures exceeding the saturated vapor pressure featured a high content of Nb and crystalline TiNb₂O₇, resulting in an ellipsoidal morphology. X-ray diffraction results also revealed that, on increasing the Nb doping amounts, the diffraction peak of the anatase TiO₂ shifted to a lower angle and the full width at half maximum decreased. This implies that the Ti atom is exchanged with the Nb atom during this process, resulting in a decrease in TiO₂ crystallinity. At a doping level of 10%, Nb-incorporated TiO₂ exhibited the best electrocatalytic activity in terms of the oxygen reduction current (i_ORR) and onset potential for the ORR (E_ORR); this suggests that 10% Nb-doped samples have the potential for enhancing electrocatalytic activity.

Functional Hybrid Micro/Nanoentities Promote Agro-Food Safety Inspection

The rapid development of nanomaterials has provided a good theoretical basis and technical support to solve the problems of food safety inspection. The combination of functionalized composite nanomaterials and well-known detection methods is gradually applied to detect hazardous substances, such as chemical residues and toxins, in agricultural food products. This review concentrates on the latest agro-food safety inspection techniques and methodologies constructed with the assistance of new hybrid micro/nanoentities, such as molecular imprinting polymers integrated with quantum dots (MIPs@QDs), molecular imprinting polymers integrated with upconversion luminescent nanoparticles (MIPs@UCNPs), upconversion luminescent nanoparticles combined with metal-organic frameworks (UCNPs@MOFs), magnetic metal-organic frameworks (MOFs@Fe₃O₄), magnetic covalent-organic frameworks (Fe₃O₄@COFs), covalent-organic frameworks doped with quantum dots (COFs@QDs), nanobody-involved immunoassay for fast inspection, etc. The presented summary and discussion favor a relevant outlook for further integrating various disciplines, like material science, nanotechnology, and analytical methodology, for addressing new challenges that emerge in agro-food research fields.