Influence of phosphorus doping on surface chemistry and capacitive behaviors of porous carbon electrode

Heteroatom doping is an effective strategy to modify the surface properties of carbon electrode, thus boosting its electrochemical performance. In this work, phosphorus (P)-doped porous carbons with high specific surface are prepared by KOH pre-activation of ultrapure anthracite and further H3PO4 activation. H3PO4 post-activation not only generates more mesoporous for a rapid ion diffusion, but also provides potential P-source for the P-doping on carbon scaffold. The increase of P-doped content significantly restrains the formation of unstable quinone and carboxylic groups, and then enhances oxidation stability of P-doped porous carbon. When evaluated as electrodes in 1 m Et4NBF4/PC, the resultant material exhibits excellent rate capability of 75% retention at 30 A g−1, extraordinary stability of 90% capacitance retention after 20000 cycles and low leakage current of less than 1.2 μA. More importantly, due to the blockage of active oxidation sites by phosphate groups, the P-doped porous carbon can stably operate at higher voltage of 3.0 V in Et4NBF4/PC compared to that of undoped porous carbon, so as to deliver a high energy density of 38.65 Wh kg−1 at 1500 W kg−1. The study offers insightful material chemistry for industrial application of H3PO4 activated porous carbon in advanced electrochemical energy storage. [Display omitted] •Phosphate groups on the carbon scaffold effectively block the active oxidation sites.•The optimized P-doped carbon demonstrates a mesoporous rate of even up to 87.48%.•P-doped carbon retains as high as 90.2% of initial capacitance over 20000 cycles.•High-voltage cycling stability and energy density are significantly improved.