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Non-noble transition metal oxides are abundant in nature. However, they are widely regarded as catalytically inert for hydrogen evolution reaction (HER) due to their scarce active electronic states near the Fermi-level. How to largely improve the HER activity of these kinds of materials remains a great challenge. Herein, as a proof-of-concept, we design a non-solvent strategy to achieve phosphate substitution and the subsequent crystal phase stabilization of metastable β-NiMoO4. Phosphate substitution is proved to be imperative for the stabilization and activation of β-NiMoO4, which can efficiently generate the active electronic states and promote the intrinsic HER activity. As a result, phosphate substituted β-NiMoO4 exhibits the optimal hydrogen adsorption free energy (−0.046 eV) and ultralow overpotential of −23 mV at 10 mA cm−2 in 1 M KOH for HER. Especially, it maintains long-term stability for 200 h at the large current density of 1000 mA cm−2 with an overpotential of only −210 mV. This work provides a route for activating transition metal oxides for HER by stabilizing the metastable phase with abundant active electronic states. Non-noble transition metal oxides are common yet typically poor hydrogen evolution catalysts due to scarce active electronic states. This work provides a route for achieving hydrogen evolution at high current densities by stabilizing a metastable NiMoO4 phase with abundant active electronic states. [ABSTRACT FROM AUTHOR]

Efficient exfoliation of layered materials has attracted considerable attention in various applications due to their superior photoelectric, physical and chemical properties. Here, we report a universal, rapid approach to prepare the two-dimensional (2D) nanosheets and zero-dimensional (0D) quantum dots (QDs) using a simple cryo-mediation liquid phase exfoliation of layered materials (graphite, MoS 2 , WS 2). The QDs decorated nanosheets 0D/2D homostructure can be subsequently formed by the self-assembly of the as-exfoliated QDs and nanosheets. The unique structural properties of the mono- or few-layer mesoporous nanosheets interspersed with QDs can expose abundant active edge sites as well as improve the conductivity, which exhibits excellent activity and stability towards electrocatalytic hydrogen evolution reaction (HER). This work offers a powerful methodology to prepare 2D homostructures from a variety of layered materials. [ABSTRACT FROM AUTHOR]

The emerging non-noble metal two-dimensional (2D) catalyst, such as MoS 2 , for the hydrogen evolution reaction (HER) is known to have an inert basal plane unless being converted to a metastable metallic phase or defect engineered. In order to take advantage of the majority of the material in such layered catalysts, fast screening of 2D catalysts with superior basal plane activity is imperative. A local electrochemical measurement method assisted by the e-beam lithography patterning was developed and applied to quantify the activity of basal planes of different layered transition metal dichalcogenides (TMDs) toward HER. This local measurement offers a robust platform to discover active TMDs fast and precisely. The construction of HER volcano plot leads to the discovery of superior basal plane active group VB metal disulfides, especially 3R-NbS 2. Interestingly, the trends found in the volcano plot imply distinctive differences in the mechanism of TMD catalysts compared to their metal counterparts. The intensive hydrogen evolution reaction in-between the basal planes drives self-nanostructuring in morphology of 3R-NbS 2. The increase in the effective surface area, and decrease in the electron-transfer resistance across the substrate and basal plane interface induced by the self-nanostructuring in turn enhances the HER performance of 3R-NbS 2. The 3R-NbS 2 clearly stands out among non-noble metal catalysts for HER. [ABSTRACT FROM AUTHOR]