▎ 摘　　要

A facile method to synthesize layered manganese oxide nanosheets was developed for the first time by using graphene oxide as a template. The in situ replacement of carbon atoms on the graphene oxide framework by edge-shared [MnO6] octahedra provides a new methodology to synthesize graphene-based two-dimensional nanomaterials. The transformation of graphene oxide into delta-type MnO2 nanosheets results in an especially high surface area (157 m(2) g(-1)), which is the highest value amongst today's MnO2 nanomaterials. Moreover, the MnO2 nanosheets demonstrated prominent capacitance (similar to 1017 F g(-1) at a scan rate of 3 mV s(-1), and similar to 1183 F g(-1) at a current density of 5 A g(-1)) and remarkable rate capability (similar to 244 F g(-1) at a high scan rate of 50 mV s(-1) and similar to 559 F g(-1) at a high current density of 25 A g(-1)), indicating their promise in high energy and power density pseudosupercapacitors.