PPTS (Pyridinium p-toluenesulfonate, >98%) Powder as Electrolyte Additive for CO2 Electroreduction (CO2RR), CCO2RREAPPTS

In electrochemical CO2 reduction (CO2RR), Pyridinium p-toluenesulfonate (PPTS, also named as Pyridine p-toluenesulfonate) is a specialized electrolyte additive primarily used to enhance the production of formic acid (formate) or syngas by acting as a proton relay and surface modifier. While less common than imidazolium-based ionic liquids, PPTS is valued for its ability to manage the local proton concentration at the cathode surface, which is critical for steering selectivity.

PPTS consists of a pyridinium cation ([PyH]+) and a p-toluenesulfonate (tosylate) anion ([OTs]-). (1) Surface-Bound Proton Donor: The pyridinium cation can adsorb onto the catalyst surface. Because the nitrogen-bound hydrogen is acidic (pKa ~5.2), the cation acts as a local proton relay. It provides protons for the multi-step reduction of CO2 more efficiently than bulk water molecules. (2) Intermediate Stabilization: The [PyH]+ cation can interact electrostatically with the negatively charged CO2'- radical or the *COOH intermediate. This interaction lowers the activation energy for the formation of C-H bonds, which is the rate-determining step for formic acid production. (3) HER Suppression: The bulky tosylate anion and the pyridinium ring can partially block the electrode surface, displacing water molecules from the inner Helmholtz plane. This "hydrophobic shielding" reduces the rate of the competing Hydrogen Evolution Reaction (HER).

The tosylate anion is not just a spectator; it contributes to the overall stability and effectiveness of the additive: (1) Solubility and Conductivity: The tosylate group ensures the salt is highly soluble in both water and organic solvents (like acetonitrile), which is useful for non-aqueous CO2 reduction. (2) Non-Interfering Anion: Unlike halides (Cl-, I-), the tosylate anion has a low tendency to specifically adsorb and poison the catalyst surface, making the electrochemical results "cleaner" and easier to interpret.

Part Number	CCO2RREAPPTS (C-CO2RR-EA-PPTS)
CAS	24057-28-1
Chemical Formula/Structure	C12H13NO3S
Appearance	White powder
Molecular Weight	251.30
Function Group	Tosylate
PPTS on Cu Catalyst	Suppresses C2+ products.
PPTS on Ag Catalyst	Shifts toward CO or Formate.
PPTS on Bi Catalyst	Enhances Formic Acid (HCOO-).
Package Grade	50 g/bottle (other package sizes, such as 100 g, 500 g, 1 kg can be supplied upon request)

References

(1）W. Nie, et al., Organic Additive-derived Films on Cu Electrodes Promote Electrochemical CO2 Reduction to C2+ Products Under Strongly Acidic Conditions, Angew. Chem. Int. Ed.. 2023, 62, e202216102. 

(2) Murugavel Kathiresan, et al., Ionic liquids as an electrolyte for the electro synthesis of organic compounds, Chem. Commun., 2015,51, 17499-17516.