Lowering the energy barrier of water dissociation is critical to achieving highly efficient hydrogen evolution in alkaline conditions. Herein, we reported mesoporous RhRu nanosponges with enhanced water dissociation behavior as a new class of high-performance electrocatalysts for alkaline hydrogen evolution reaction (HER). The obtained nanosponges have a binary alloy structure (fcc) and a highly porous structure with high surface area. Our RhRu catalyst displayed an outstanding HER activity with an overpotential of 25 mV at 10 mA cm–2 and a Tafel slope of 47.5 mV dec–1 in 1.0 M KOH, which significantly outperformed that of commercial Pt/C catalyst and was even comparable to the classic Pt/metal (hydro)­oxide catalysts. Density functional theory (DFT) calculations disclosed that charge redistribution on the RhRu alloy surface enabled tuning of the Ru d-band center and then promoted the adsorption and dissociation of water molecules. Based on the experimental results and theoretical modeling, a bifunctional mechanism contributed to the remarkable alkaline HER activity on the RhRu catalyst surface.

Exploiting new interface-active solid catalysts is crucial to construct efficient Pickering emulsion systems for biphasic catalysis. In this work, ultrathin g-C3N4 nanosheets (g-C3N4-NSs) were developed as a new solid emulsifier to directly position catalytic sites at oil–water interfaces for improving the reaction efficiency of a biphasic reaction. Exemplified by a metal-involved biphasic reaction of nitroarenes reduction, the developed Pd/g-C3N4-NSs catalyst with Pd nanoparticles loaded on the surface of g-C3N4-NSs exhibited excellent activity with a catalytic efficiency of 1220 h–1. Such activity was 4.2 and 17.9 times higher than those of Pd/g-C3N4-bulk and the ordinary Pd/C8-SiO2 catalyst, respectively. Also, in the biphasic oxidation reaction of alcohols, Pd/g-C3N4-NSs achieved a 2.3-fold activity enhancement. It was found by analyzing the solidified emulsion droplets that the Pd/g-C3N4-NSs catalyst was parallelly assembled at the oil–water interfaces. Because of the ultrathin thickness of g-C3N4-NSs, such a unique interfacial assembly behavior allowed precise positioning of Pd nanoparticles at the oil–water interfaces. As a result, the oil-soluble reactant could directly react with the water-soluble reactant at the oil–water interface hosting the Pd nanoparticles. Our elaborately designed reaction interface was believed to substantially avoid the diffusion barrier between oil-soluble and water-soluble reactants and then to significantly enhance the reactivity of biphasic reactions. This work highlights the importance of the interfacial location of catalytic sites in biphasic catalysis.

Through postreducing the pore size of a mesoporous shell, Hoveyda− Grubbs 2nd catalyst was successfully encapsulated within yolk−shell structured silica, leading to a heterogeneous catalyst for olefin metathesis. Such a catalyst exhibits much higher activity than the reported encapsulated catalysts in olefin ring-closing metathesis and cross metathesis. This excellent activity can be attributed to the combination of a hollow structure in the interior and permeable mesopores in the shells. This catalyst shows good recyclability, highlighted by eight cycles of reaction. This work not only supplies an excellent heterogeneous olefin metathesis catalyst but also demonstrates that yolk−shell structured silica materials can be used as an innovative scaffold to encapsulate homogeneous catalysts.

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