Production of Ammonium Polysulfide

In a recent patent Anastasijevic and coworkers11 have described the use of electrochemical promotion to produce ammonium polysulfide, (NH4)2SX, is an efficient manner. The novel electrochemically promoted process leads to faradaic efficiency, A, values of at least four11 and p(=r/r0) values of at least eight.11 

The catalytic (no net charge transfer) reaction which is electrochemically promoted is  

The ammonium polysulfide, (NH4)2SX (with x=2 to 6) is produced in an electrochemical cell where aqueous ammonium sulfide, (NH4)2S, solution is supplied as electrolyte. The cell comprises an anode and a gas diffusion carbon cathode over which gaseous 02 is supplied in contact with the electrolyte.11 The cell operated continuously at pressures up to 60 bar. The applied potential, UWc was 0.01 to 5 V. Pronounced electrochemical promotion behaviour was observed at Uwc values as low as 0.02 V with a current 1=0.5 A. 

This new NEMCA process underlines the potential importance of electrochemical promotion in industrial aqueous electrolyte systems. 

This exciting work carried out by Bjerrum and coworkers12 in the experimental set up of Fig. 10.6 is truly remarkable for several reasons. The major difference from all electrochemical promotion studies surveyed in this 

---