Optimization of electrocatalysts' geometry structure for making them stabilized and more active sites exposed or accessible is one of keys to design the electrocatalysts with highly active and durable oxygen reduction reaction (ORR) performance. Herein, we designed and reported a novel metal-sulfide-based host-guest electrocatalyst with the apparently-instable Cu2S nanoparticles (NPs) cage-confined into chalcogenide semiconductor zeolite (RWY). Such in-situ-formed composite electrocatalyst was built by diffusing Cu2+ ions into the nanocages of RWY via a facile ion exchange and subsequent etching processes. The obtained composite electrocatalysts with various amount of Cu2S (denoted as Cu2S@ RWY-x%, x represents for weight percent of Cu2S) display superior ORR activity, especially for Cu2S@ RWY-48.6% showing the best catalytic activities in an alkaline solution with the onset potential of 0.90 V (vs. RHE), quasi-four-electron transfer pathway, and small Tafel slope (69 mV/dec). Importantly, the superior ORR performance from the apparently-inactive guest Cu2S NPs is for the first time explored, which is ascribed to the host-induced stabilization and the optimized balance between catalysts' loading and their accessibility. This work holds great promising for exploring other cage-confined metal-chalcogenide NPs for the applications in other electrocatalytic fields. (C) 2018 Elsevier Ltd. All rights reserved.