In-situ H2 production via low temperature decomposition of ammonia: Insights into the role of cesium as a promoter

Abstract

RutheniumCesium Promoter a b s t r a c t Cesium-promoted ruthenium nanoparticles supported on multi-walled carbon nanotubes catalysts are shown to be highly active for hydrogen production by ammonia decomposition. Its low temperature activity is significantly improved as the cesium loading increases, reducing the activation energy from 96.7 kJ/mol in the absence of cesium to 59.3 kJ/ mol with a cesium/ruthenium molar ratio of 3. Hydrogen production was observed to proceed below 590 K which represents a breakthrough towards the use of ammonia as chemical storage for in-situ hydrogen production on fuel cells. The catalytic enhancement is shown to be due to the electronic modification of ruthenium by the electron donating cesium promoter located on the ruthenium surface and in close proximity on the CNT surface. However, higher promoter loadings above a cesium/ruthenium ratio of 3 leads to ammonia inaccessibility to the catalytic active sites.

H2 Production via Ammonia Decomposition Using Non-Noble Metal Catalysts: A Review

“…Co(en) 3 MoO 4 ), a higher activity and stability was achieved compared with the use of the equivalent monometallic salts. It is likely that Co and Mo have a strong interaction in the Co(en) 3 MoO 4 salt and the higher activity can be attributed to a higher content of the Co 3 Mo 3 N active species.…”

“…Co(en) 3 MoO 4 ), a higher activity and stability was achieved compared with the use of the equivalent monometallic salts. It is likely that Co and Mo have a strong interaction in the Co(en) 3 MoO 4 salt and the higher activity can be attributed to a higher content of the Co 3 Mo 3 N active species. The stability of the bimetallic catalyst using Co(en) 3 MoO 4 salt as metal precursor did not vary after 1200 h on stream, whereas the activity of the monometallic cobalt catalyst declined over this period, possibly due to the migration of cobalt to the tetrahedral c-Al 2 O 3 sites of the support forming inactive CoAl 2 O 4 .…”

“…It can be produced sustainably via water splitting using surplus renewable energy to balance the grid demands. However, the potential of the called ''hydrogen economy'' is currently limited by the inability to store hydrogen in a safe and economical manner with a sufficiently high density without using controversial high pressures [3].…”

“…Ru h À1 at 370°C) [3,17,19,20]. Furthermore, the synergetic effect of cesium and the [5][6][7][8][9][10].…”

Hydrogen Generation from Additive-Free Formic Acid Decomposition Under Mild Conditions by Pd/C: Experimental and DFT Studies

“…Ammonia decomposition has been also studied at temperatures below 500 K showing a significant reduction in activation energy when using carbon nanotubes catalysts promoted with cesium [14]. Metal hydrides such those of Mg-Al-Fe has been reported to achieve a maximum rate of 499.5 ml min −1 g −1 of hydrogen at 25 °C for Mg 60 -Al 30 -Fe 10 (wt%) in 0.6 mol l −1 NaCl solution [15].…”