RuO2@MoO <i>x</i> heterostructure for high-performance and quasi-solid-state biodegradable supercapacitor

With the rapid development of wearable electronics and implantable medical devices, energy storage systems combining high-performance and biodegradability have attracted increasing attention. In this study, an oxide layer was in situ constructed on the surface of molybdenum (Mo) foil via high-temperature annealing, followed by uniform coating of ruthenium oxide (RuO2) nanoparticles, fabricating RuO2@MoOx heterostructure (HS). Furthermore, a quasi-solid-state biodegradable supercapacitor (SCs) was assembled with RuO2@MoOx HS as an electrode, achieving a specific capacitance of 544.6 F/g, along with an areal capacitance of 0.98 F/cm2 and a volumetric capacitance of 497.46 F/cm3 at 1 A/g. The device also exhibited an impressive cycle stability, retaining 85.9% of its capacitance after 2000 cycles, and an attractive energy density of 294.8 W h/kg at 987 W/kg. Moreover, the device underwent complete degradation in 5% hydrogen peroxide solution within 8 days, demonstrating excellent environmental responsiveness and biocompatibility. This work provides an effective strategy for the design and development of high-performance, biodegradable SCs and showcases promising application prospects in transient electronics and implantable biomedical systems.