EDTMPA (Ethylenediamine Tetramethylenephosphonic Acid, >98%) Powder as Electrolyte Additive for CO2 Electroreduction (CO2RR) and Zinc-Bromine Flow Battery, CCO2RRZBFBEAEDTMPA

In electrochemical CO2 reduction (CO2RR), EDTMPA (Ethylenediamine tetra(methylene phosphonic acid)) is a multi-functional electrolyte additive used primarily as a metal ion sequestrant, surface modifier, and HER (Hydrogen Evolution Reaction) suppressor.

Sequestration of Impurity Ions: The most critical role of EDTMPA is protecting the catalyst from poisoning. Even high-purity aqueous electrolytes (KHCO3) often contain trace amounts of transition metal ions (like Fe2+, Zn2+, or Pb2+). During long-term electrolysis, these ions deposit onto the cathode surface. EDTMPA is a powerful chelating agent that binds to these trace metal impurities in the bulk electrolyte, preventing them from electrodepositing onto the active catalyst. This is essential for maintaining the selectivity of Copper or Silver catalysts over long periods. Suppression of the Hydrogen Evolution Reaction (HER): EDTMPA helps steer the reaction away from water splitting and toward CO2 conversion. The large, negatively charged EDTMPA molecules adsorb onto the electrode surface. This creates a "steric barrier" that hinders the approach of water molecules to the active sites.  By limiting the availability of protons (H+) at the surface, EDTMPA effectively suppresses the HER, thereby increasing the Faradaic Efficiency (FE) for CO2 reduction products.

While for zinc-bromide flow battery, EDTMPA can be mainly used to control zinc morphology and prevent dendrite growth, which are the leading causes of short-circuiting and capacity fade in these systems. Zinc tends to deposit unevenly, forming needle-like "dendrites" that can puncture the membrane. EDTMPA molecules adsorb onto the high-energy sites (the "tips") of growing zinc crystals. This creates a local barrier that forces the zinc ions (Zn2+) to deposit on flatter, lower-energy areas instead. This results in a smooth, dense, and uniform zinc plating layer rather than a porous or "mossy" structure, significantly extending the cycle life of the battery. (2) Chelating and Complexing Zn2+. The four phosphonic acid groups in EDTMPA provide strong binding sites for zinc ions. EDTMPA forms stable complexes with Zn2+ in the aqueous electrolyte. This effectively "regulates" the concentration of free zinc ions available at the electrode surface during charging. By controlling the rate of ion delivery to the cathode, EDTMPA helps prevent the local ion depletion that usually triggers unstable, non-planar growth.

Part Number	CCO2RREAEDTMPA (C-CO2RR-EA-EDTMPA)
CAS	1429-50-1
Chemical Formula/Structure	C6H20N2O12P4
Appearance	White powder
Molecular Weight	436.12
EDTMPA on Cu Catalyst	Stabilizes Cu+ species and promote the formation of multicarbon (C2) products like ethylene by preserving oxide-derived surface features.
EDTMPA on Ag Catalyst	Suppresses HER and Enhances the FE for Carbon Monoxide (CO), especially at low overpotentials where impurities usually dominate.
EDTMPA on Bi/Sn Catalyst	Buffers local pH and Helps maintain the high local pH required to stabilize Formate intermediates.
EDTMPA for Zinc-Br Flow Battery	1. Prevents short-circuits, allowing for thousands of charge/discharge cycles. 2. Slightly increases overpotential, but results in a more stable discharge voltage profile. 3. Protects the zinc anode from self-discharge (corrosion) during standby periods.
Package Grade	25 g/bottle (other package sizes, such as 100 g, 500 g, 1 kg can be supplied upon request)

References

(1）Z. Han, et al., Steering surface reconstruction of copper with electrolyte additives for CO2 electroreduction, Nature Communications, 2022, 13, 3158. 

(2) W. Xia, et al., Multidentate Chelating Ligands Enable High-Performance Zinc-Bromine Flow Batteries, Angew Chem Int. Ed., 2025, 64, e202418669.