Biodegradable Mg-Mo₂C MXene Air Batteries for Transient Energy Storage

Primary batteries are the fundamental power sources in small electronic gadgets and bio/ecoresorbable batteries. They are fabricated from benign and biodegradable materials and are of interest in environmental sensing and implants because of their low toxicity toward the environment and human body during decomposition. However, current bio/ecoresorbable batteries suffer from low operating voltages and output powers because of the occurrence of undesired hydrogen evolution reactions (HERs) at cathodes. Herein, Mo₂C MXene was used as a cathode to achieve high operating voltage and areal power. Mo₂C provides energy barriers for HERs in alkaline solutions, and such barriers suppress HERs and allow the oxygen reduction reaction to dominate at the cathode. The fabricated battery exhibits an operating voltage and areal power of 1.4 V and 0.92 mW cm^-2, respectively. Degradation tests show that the full cell completely degrades within 123 days, leaving only Mo fragments from the electrode and biodegradable encapsulation. This study provides insights into bio/ecoresorbable batteries with high power and operating voltage, which can be used for environmental sensing.