High surface area niobium oxides as catalysts for improved hydrogen sorption properties of ball milled MgH2

Abstract We report, high surface area (up to 200 m 2 /g) nanocrystalline niobium oxide (so called p-Nb 2 O 5 ) synthesized by ‘chimie douce’ route and its importance in enhancing the hydrogen sorption properties of MgH 2 . p-Nb 2 O 5 induces faster kinetics than commonly used commercial Nb 2 O 5 (c-Nb 2 O 5 ) when ball milled with MgH 2 (named (MgH 2 ) catalyst ) by reducing the time of desorption from 35 min in ( Mg H 2 ) c-N b 2 O 5 to 12 min in ( Mg H 2 ) p-N b 2 O 5 at 300 °C. The BET surface area of as-prepared Nb 2 O 5 was tuned by heat treatment and its effect on sorption properties was studied. Among them, both p-Nb 2 O 5 and Nb 2 O 5 :350 (p-Nb 2 O 5 heated to 350 °C with a BET specific surface area of 46 m 2 /g) desorb 5 wt.% within 12 min, exhibiting the best catalytic activity. Furthermore, thanks to the addition of high surface area Nb 2 O 5 , the desorption temperature was successfully lowered down to 200 °C, with a significant amount of desorbed hydrogen (4.5 wt.%). In contrast, the composite ( Mg H 2 ) c-N b 2 O 5 shows no desorption at this “low” temperature.