The applications of hydrogels are severely limited by their weak mechanical properties. Despite recent significant progress in fabricating tough hydrogels, it is still a challenge to realize high stretchability, toughness, and recoverability at the same time in a hydrogel. Herein, we develop a novel class of dual physically cross-linked (DPC) hydrogels, which are triggered by clay nanosheets and iron ions (Fe 3+ ) as cross-linkers. First, clay nanosheets induce the formation of the first cross-linking points through the interaction of hydrogen bonds with poly(acrylamide-co-acrylic acid) (PAm-co-Ac) chains. Then the secondary cross-linking points are introduced by ionic coordinates between Fe 3+ and −COO− groups of PAm-co-Ac polymer chains. The mechanical properties of DPC hydrogels can be tuned readily by varying preparation parameters such as clay concentration, Fe 3+ concentration, and molar ratio of Ac/Am. More importantly, the optimal DPC hydrogels possess high tensile strength (ca. 3.5 MPa), large elongation (ca. 21 times), remarkable toughness (ca. 49 MJ m −3 ), and good self-recoverability (ca. 65% toughness recovery within 4 h without any external stimuli). Thus, this work provides a promising strategy for the fabrication of novel tough hydrogel containing a dual physical cross-linked network.

Oxygen-deficient anatase TiO2@C nanospindles are realisedviathe hydrogenation and carbon coating of TiO2nanospindles. The produced electrodes exhibit an enhanced electrochemical performance for Li storage.

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