1 butyl 3 methylimidazolium trifluoromethanesulfonate

All chemicals of reagent grade quality were obtained from commercial sources and used without further purification. CoSO₄·6H₂O (50.0 mmol), Ce(NO₃)₃·6H₂O (50.0 mmol), NiSO₄·6H₂O (50.0 mmol), and CuSO₄·5H₂O (50.0 mmol) were purchased from Merck (Milipore, Darmstadt, Germany). 1-Hydroxyethane-1,1-diphosphonic acid, sodium hydroxide, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium nitrate, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methyl-imidazolium chloride, 2,6-dimethylphenol, and 4,4′-dihydroxybiphenyl were obtained from Sigma-Aldrich Chemie GmbH (München, Germany), and urea from Alfa Aesar (Karlsruhe, Germany).

PEDOT:PSS solution (Clevios PH 1000, PEDOT:PSS weight ratio = 1:2.5 and concentration by mass = 1.3%) was purchased from Heraeus. Formamide, sodium formaldehyde sulfoxylate (SFS), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM-OTf) or 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (BMIM-TFSI) were purchased from Sigma-Aldrich. All chemicals were used as received without further purification. The chemical structures of ionic liquids are shown in Scheme 1.

1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide
(BMIM-NTf₂, 99%) and 1-butyl-1-methylpyrrolidinium triflate
(BMPYRR-OTf, 99%) were purchased from IoLiTec and used as received.
1-Butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM-OTf, 97%),
K₂PtCl₄ (99.9%), polyvinylpyrrolidone (PVP,
MW = 55,000), ethylene glycol (99.8%), and Fe(NO₃)₃•9H₂O (98%) were all purchased from Sigma-Aldrich
and used as received. 1-Butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide
(BMPYRR-NTf₂, 98%) was purchased from TCI Chemicals and
used as received. Acidified water at different pH levels was prepared
by diluting a nitric acid solution (Supelco, 68–70%) with deionized
(DI) water. The pH values were verified by a pH meter (Jenway 3510).