Highly flexible pseudocapacitors of phosphorus-incorporated porous reduced graphene oxide films

We demonstrate hierarchically structured, phosphorous (P)-incorporated reduced graphene oxide (HPG) films prepared by a vacuum-filtrated and ice-frozen assembly, freeze-drying and thermal treatment for all solid-state flexible pseudocapacitors. The porous morphology is originated from the interconnected networks of graphene layers and the surface roughness is reduced by the P doping, which results in improving the electrochemical performances. The P=O sites of C-P=O bonding acting as electro-active sites of HPG film are identified by XPS spectra and their charge storage behavior is monitored by in-situ and ex-situ spectrochemical analyses. The HPG film achieves the specific capacitance of 149 F g⁻¹, the capacitance retention of 90.8% from 1 to 30 A g⁻¹, and the cyclic stability of 94.2% over 1000 charging/discharging cycles. Moreover, the pseudocapacitive performances of the HPG films are preserved at the bending state of 120° angle. These excellent electrochemical behaviors are attributed to the unique hierarchical structure and the formation of electro-active of P=O sites by heteroatom doping.