Free-standing black phosphorus foils for energy storage and catalysis.

Few-layer black phosphorus (BP) is a two-dimensional material that has attracted intensive attention for application in energy storage and catalysis due to its large surface area, and good electrical and thermal conductivity. Herein we demonstrate a comparable study of black phosphorus electrochemical exfoliation in various anion medium of tetrabutylammonium salts (TBAX, where X is -PF6, -BF4, -ClO4) in dimethylsulfoxide (DMSO). Based on the morphological and structural analysis we show that the TBAPF6/DMSO medium was specifically appropriate for the production of high-quality BP nanosheets with micrometer lateral size and thickness of about ~2.4 nm. TBAPF6/DMSO-processed few-layer BP exhibits enhanced HER catalytic activity compared with samples exfoliated with the assistance of BF4- and ClO4- ions. Finally, we demonstrate the fabrication process of flexible free-standing BP films and further their performance in the all-solid-state supercapacitor device.