Hierarchical nanoporous metal/metal-oxide composite by dealloying metallic glass for high-performance energy storage

•Free-standing nanoporous Y–Co–Ni is fabricated by dealloying Al85Y6Ni6Co3 metallic glass.•The nanoporous Y–Co–Ni exhibits a hierarchical structure with bimodal pores and surface metal oxide whiskers.•The formation of bimodal pores and the oxidation of the ligament surface occur simultaneously.•The nanoporous metal/metal-oxide composite exhibits a high areal capacitance.

A free-standing nanoporous YNiCo metal/metal-oxide composite with hierarchical porosity is fabricated by chemically dealloying Al85Y6Ni6Co3 metallic glass in alkaline solutions. The mixed core–shell-like metal/metal-oxide structure formed during dealloying due to the active properties of these metals. Time-dependent etching experiments suggest that the formation of large and small pores occur simultaneously, which may be related to the different dissolution rate of Al at different sites. The nanoporous composite with a highly conductive metal core exhibits a high areal capacitance. Moreover, this strategy can be extended to fabricate other nanoporous composites considering that the composition of metallic glass can be easily tuned.