Fashioned Performance-Boosting On-Chip Planar Microsupercapacitors Based on Chemical Vapor Deposition Graphene and Graphene Quantum Dot Heterostructures

Planar microsupercapacitors (PMSCs) are emerging micro–nano energy storage devices that greatly promote the rapid development of portable integrated electronic systems. Graphene and graphene quantum dots (GQDs), as electrode materials, exhibit excellent performance in the field of PMSCs. Yet there remains considerable scope for improvement in the overall electrochemical performance of PMSCs to meet practical applications. Herein, a layer-by-layer assembled silicon dioxide/chemical vapor deposition (CVD) monolayer graphene/GQD heterostructure electrode was developed, which can effectively tackle the aforementioned critical challenges, enabled by unique CVD and liquid–air interfacial self-assembly methods. The heterostructure electrode features a GQD layer, which provides abundant electrochemically active sites and edge defects and contributes to the pseudocapacitance and the underlying monolayer graphene, providing exceptional electrical conductivity and extremely short ion transport channels. The PMSCs fabricated through photolithography show excellent rate capability with an ultrahigh scan rate of 10,000 V s –1, which exceeds conventional supercapacitors by 4 orders of magnitude, ultrafast frequency response capability with a characteristic frequency of 51,379 Hz and a corresponding relaxation time constant of 19.46 μs, and ultrahigh power output capability with a power density of 14.76 W cm –3 that is equivalent to electrolytic capacitors. This work could build up original frameworks to satisfy the application requirements of portable miniaturized high-performance energy storage devices.