Electrochemical stability and capacitance of in-situ synthesized Prussian blue on thermally-activated graphite

Abstract

Abstract: The search has been on for years to find at least, a stable, high surface area scaffold for Prussian blue (PB) and its analogs. If successful, PB’s vast potential applications could be practicable. This, is besides other innate issues with PB such as poor cycle stability, low electronic conductivity to mention a few. For the first time, a stable Prussian blue@thermally activated graphite felt scaffold, with cycling stability of 2100 cycles, from − 0.5 to 1.3 V, and in 1 M KCl, for at least 36 h is reported. At the end of 2100 CV cycles, sample capacitance more than tripled (381 mF cm−2 compared to 120 mF cm−2 at start of experiment). These properties suggest a practical ion-sieve for specific cation removal from contaminated water. Two new synthesis protocols were employed to achieve this: (a) a first time, single solution PB synthesis without externally applied potential, current or even elevated temperature and (b) a two-step solution-dipping process not involving acidic conditions. PB from both protocols exhibited similar electrochemical characteristics even though the electron relay paths along their charge transfer complexes are different. When probed for its HOMO characteristics, the PB@thermally-treated graphite showed no significant electronic difference from the thermally-treated felt scaffold, suggesting non-compromise of the treated graphite by the PB. Besides cation removal, the electrochemical and electronic properties of these PB@treated graphites suggest multiple electrochemical, non-electrochemical and electronic applications with intact structural and functional integrity. Graphic abstract: Thermal activation of graphite felt increases capacitance while Prussian blue formation, either by metal-aided catalysis or the solution-dip method, further increases capacitance for the composite matrix.[Figure not available: see fulltext.].