Boosted charge transfer in p-n heterojunctions LaMoO3/GQDs negative electrode for all-solid-state asymmetric supercapacitor

The low energy density of asymmetric supercapacitor (ASC) is limited by the negative electrodes; thus, to further increase the energy density of ASCs, it is necessary to optimize the design of the negative electrode and the device. Constructing p-n heterojunctions may be a viable approach for enhancing the performance of the negative electrode, as it enhances the driving force for the built-in charge transfer and thereby it is beneficial for the charge transfer dynamics. Herein, we attempted to configure graphene quantum dots (GQDs) and LaMoO3 as a p-n heterojunction via one-step hydrothermal method, which shows outstanding capacitance performance. The specific capacitance of the LaMoG-3 (1396 F g−1 at 1 A g−1) was higher than the theoretical value for molybdenum trioxide (1256 F g−1). Moreover, the ASC is successfully assembled all-solid-state ASC with GQDs/Mn3O4 as the positive electrode and LaMoG-3 as the negative electrode. The as-fabricated ASC exhibited an ultra-high density of 235.8 Wh kg−1 and a power density of ~1000 W kg−1. One device can light the LED indicator for more than 11 min after only charging for 5 min. The above-mentioned results will open up promising research pathways for achieving excellent energy density and high power density.