Developing efficient electrocatalysts for alkaline water electrolysis is central to substantial progress of alkaline hydrogen production. Herein, a Ni5P4 electrocatalyst incorporating single‐atom Ru (Ni5P4‐Ru) is synthesized through the filling of Ru3+ species into the metal vacancies of nickel hydroxides and subsequent phosphorization treatment. Electron paramagnetic resonance spectroscopy, X‐ray‐based measurements, and electron microscopy observations confirm the strong interaction between the nickel‐vacancy defect and Ru cation, resulting in more than 3.83 wt% single‐atom Ru incorporation in the obtained Ni5P4‐Ru. The Ni5P4‐Ru as an alkaline hydrogen evolution reaction catalyst achieves low onset potential of 17 mV and an overpotential of 54 mV at a current density of 10 mA cm‐2 together with a small Tafel slope of 52.0 mV decade‐1 and long‐term stability. Further spectroscopy analyses combined with density functional theory calculations reveal that the doped Ru sites can cause localized structure polarization, which brings the low energy barrier for water dissociation on Ru site and the optimized hydrogen adsorption free energy on the interstitial site, well rationalizing the experimental reactivity.

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A straightforward and very efficient pathway has been reported for the synthesis of a functional derivative of ε-caprolactone, i.e. 5-ethylene ketal ε-caprolactone. This new monomer has been homopolymerized and copolymerized with ε-caprolactone in a well-controlled manner, strongly suggesting absence of any side reactions. Deacetalization of the polyester chains is complete and reduction of the ketone groups into hydroxyl groups as well. No chain scission is observed to occur in the course of these two derivatization reactions. Thus, aliphatic polyesters bearing either ketone pendent groups or hydroxyl pendent groups can be easily prepared, which raises new application prospects. These materials proved to be easily redispersed in an aqueous medium. They form stable colloidal nanodispersions (e.g. 100 nm). These suspensions are stable more than 48 h at room temperature and may be viewed as potential drug colloidal vectors with a core−shell like structure. Different types of reactive groups on the surface of these nanoparticulate vectors are indeed available to the binding of species selected for molecular recognition and drug targeting. For instance, the well-known reactivity of ketones toward primary amines is a direct route to attach peptides onto biodegradable and biocompatible aliphatic polyesters. Poly(ε-caprolactone) with hydroxyl groups reactive toward triethylaluminum provides a macroinitiator for lactone and lactide polymerization, so that biodegradable and biocompatible functional comb, graft, and dendritic aliphatic polyesters can now be synthesized.

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