A novel hybrid, composed of Co3O4 quantum dots supported on Ti3C2Tx (MXene) nanosheets, exhibits a strong synergetic effect, and shows superior lithium storage (capacity = 766.5 mA h g-1 at 2 A g-1 after 400 cycles) and oxygen evolution (overpotential = 340 mV at 10 mA cm-2) activities.