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.