Facilitated transport of ammonia in ultra-thin Prussian Blue membranes with potential-tuned selectivity

Here we report on tunable ammonia transport through ultrathin Prussian Blue (PB) membranes facilitated with protonic carrier. Continuous gas-tight 15–50 nm Prussian Blue layers were prepared by cyclic electrodeposition on porous gold/anodic aluminum oxide supports. The membranes reveal fast ammonium transport with NH 3 permeance exceeding 0.3 m 3 (STP) m - 2 bar -1 h -1 , ultimate ideal NH 3 /H 2 selectivity attaining 40 and NH 3 /N 2 selectivity over 100. In mixed-gas separation thermodynamically-favored sorption leads to additional NH 3 /H 2 selectivity rise to ~70. Facilitation of NH 3 transport occurs upon its conversion to NH 4 + maintaining the electroactivity of the selective layer and reversibly tuned by electrochemical framework loading. Engagement of the protonation step is supported with Raman spectroscopy and close values of NH 3 diffusion coefficients measured in gas permeation experiments and NH 4 + diffusion coefficient determined by electrochemical impedance spectroscopy in liquid phase. The impact of water vapors partial pressure as backward protonic carrier on NH 3 transport efficiency is exposed and discussed. • Dense Prussian Blue (PB) layer was electrochemically deposed on anodic alumina support. • PB membranes demonstrate NH 3 /H 2 mixed-gas selectivity up to 70 and NH 3 permeance >0.3 m 3 /(m 2 ·bar·h). • Ammoina facilitated transport is realized due to transformation NH 3 into NH 4 + form. • Gas transport properties of membrane can be tuned by PB loading with NH 4 + cations.