Flattening bent Janus nanodiscs expands lattice parameters

Nanoscale lattice parameter engineering is a potentially powerful tool for tailoring the electronic properties of nanomaterials. The nascent strain in juxtaposed hetero-interfaces of nanocrystals was recently shown to substantially affect the energy states of the exposed surfaces and improve catalytic activity; however, practical implementations of this design strategy are rare. Herein, we report that Rh₃S₄ and Cu₃₁S₁₆ can be combined to produce a bent Janus-type nanodisc in which the surface strain can be controlled precisely by modulating the curvature. These nanodiscs are conveniently prepared by replacing copper with rhodium in Cu₃₁S₁₆ via anisotropic cation exchange, which induces lattice strain and bends the nanodiscs. Flattening the Rh₃S₄/Cu₃₁S₁₆ nanodisc leads to a unique surface lattice structure and affords superior electrocatalytic performance in the hydrogen evolution reaction. We demonstrate a general and straightforward strategy for controlling the lattice strains in hetero-nanostructures and for systematically improving their catalytic performance.