Decoupling Electron- and Phase-Transfer Processes to Enhance Electrochemical Nitrate-to-Ammonia Conversion by Blending Hydrophobic PTFE Nanoparticles within the Electrocatalyst Layer

Electrochemical upcycling of nitrate into ammonia at ambient conditions offers a sustainable synthesis pathway that can complement the current industrial NH₃ production from the Haber–Bosch process. One of the key rate-limiting steps is the effective desorption of gaseous or interfacial bubble products, mainly NH₃ with some minor side products of nitrogen and hydrogen, from the electrode surfaces to sustain available sites for the NO₃⁻ reduction reaction. To facilitate the gaseous product desorption from the catalytic sites, hydrophobic polytetrafluoroethylene (PTFE) nanoparticles are blended within a CuO catalyst layer, which is shown to eliminate the undesirable accumulation and blockage of electrode surfaces and largely decouples the electron- and phase-transfer processes. The NH₃ partial current density normalized by the electrochemically active surface area (ECSA) increases by nearly a factor of 17.8 from 11.4 ± 0.1 to 203.3 ± 1.8 mA cm⁻²_ECSA. The DFT and ab-initio molecular dynamics simulations suggest that the hydrophobic PTFE nanoparticles may serve as segregated islands to enhance the spillover and transport the gaseous products from electrocatalysts to the PTFE. Thus, a higher ammonia transfer is achieved for the mixed PTFE/CuO electrocatalyst. This new and simple strategy is expected to act as inspiration for future electrochemical gas-evolving electrode design.