Zhuangzhi Wu

Enhanced hydrogen evolution catalysis from osmotically swollen ammoniated MoS2

An osmotically swollen ammoniated MoS2 electrocatalyst for hydrogen evolution is developed via a simple hydrothermal route for the first time. The applied relatively high temperature and pressure promote the diffusion of NH4+ ions into MoS2 lamellar structures, leading to the formation of ammoniated MoS2 with remarkable lattice expansion. The insertion of NH4+ ions induces a great enhancement in the electrical conductivity of MoS2, resulting in an excellent activity for the hydrogen evolution reaction with a small Tafel slope of 45 mV dec−1, which is amongst the best recorded for MoS2-based catalysts, making it a very promising electrocatalyst to replace Pt-based ones.

Phase engineering of a multiphasic 1T/2H MoS2 catalyst for highly efficient hydrogen evolution

Molybdenum disulfide (MoS2) has attracted much attention as a promising electrocatalyst for the hydrogen evolution reaction (HER). Although tremendous efforts have been made to enhance the HER performance of MoS2, the functional design of its intrinsic structures still remains challenging. In this work, a highly active and stable multiphasic catalyst (1T/2H MoS2) is developed through a facile hydrothermal route, in which the 1T phase is induced by the intercalation of guest ions and molecules, and the concentration of the 1T phase can be controlled by adjusting the preparation temperature. The existence of the 1T phase provides more active sites and better conductivity for the HER, resulting in an excellent activity with a small Tafel slope of 46 mV dec−1. More importantly, the integration with the 2H phase is beneficial to the stabilization of the metastable 1T phase, ensuring the excellent durability of 1T/2H MoS2.

Hydrogen evolution catalyzed by cobalt-promoted molybdenum phosphide nanoparticles

Co-promoted molybdenum phosphide nanoparticles have been successfully prepared and explored for the first time as a cost-effective electrocatalyst for hydrogen evolution reaction (HER). The as-developed catalyst demonstrates excellent HER activity with a small Tafel slope of 50 mV dec−1 which is among the best records reported for MoP-based catalysts. The addition of Co not only reduces the particle size of the MoP-based catalyst and promotes the charge transfer, but also enhances the intrinsic activity of each active site, paving the way for optimizing the HER performances of ternary or multiple transition metal phosphide catalysts.

Ultrasonic-assisted preparation of metastable hexagonal MoO3 nanorods and their transformation to microbelts

Metastable hexagonal h-MoO(3) nanorods were synthesized by a simple sonochemical method, and then were transformed into thermodynamically stable a-MoO(3) microbelts by calcination. The obtained samples were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). It was found that the as-prepared h-MoO(3) nanorods were of 0.2-1.2 μm in width and 1-6 μm in length. A possible formation and growth mechanism of hexagonal MoO(3) nanorods is proposed, in which ultrasound plays a crucial role and cannot be ignored. Moreover, the effect of temperature on the transformation process by calcination is investigated and a possible growth process of microbelts is also discussed.

Influence of Carbon on Molybdenum Carbide Catalysts for the Hydrogen Evolution Reaction

The influence of carbon on molybdenum carbide catalysts for the hydrogen evolution reaction (HER) is discussed. The carbon content is adjusted by varying the molar ratio of molybdenum and glucose sources and the holding time in the carbonization process. The carbon plays a crucial role in the determination of phase formation, surface area, and electrical resistance, which are associated with the final HER activity. There is a contradiction between the reduced active sites and improved electrical resistance that results from the reduced content of carbon, and a balance can be achieved with a holding time of 9 h to provide the best HER activity with a low Tafel slope of 55 mV dec−1 and a high exchange current density of 0.047 mA cm−2. Importantly, the transformation of the order of the free carbon improves the electrical conductivity remarkably to result in a great improvement in the final HER activity.