Milling induced surface modification of V-based catalyst to improve sorption kinetics of KSiH3: An XPS investigation. (25th December 2022)

• Record Type: Journal Article
• Authors: Sharma, Shashi; Singh, Rini; Ichikawa, Takayuki; Jain, Ankur; Agarwal, Shivani
• Is Part Of: International journal of hydrogen energy. Volume 47:Number 99(2022)
• Page Start: 41911
• Page End: 41919
• Publication Date: 2022-12-25
• Subjects: Hydrogen storage -- Metal hydrides -- Silanide -- KSiH3 -- Catalyst -- Activation energy; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2022.04.083
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Hydrogen as an energy carrier has shown promises for future energy infrastructure. Due to its light weight and explosive nature, hydrogen need to be stored in safe and efficient way. The storage in solid state materials has been proposed as the safest method, which can store hydrogen through chemical bonding. Among several studied materials so far, KSiH3 is one of the leading contender with a total hydrogen capacity of 4.3 wt %, which is more than what is offered by its rivals such as BCC hydrides or AB5 type hydrides. However, the high activation energy slows down the hydrogen charging/discharging rate and allow the working only at higher temperatures (∼200 °C). The kinetics of hydrogen absorption and desorption intensely improved by the addition of a catalyst. In this work, vanadium based catalysts are added to KSiH3 system to modify the surface and to enhance the kinetics of this system. Specially, V2 O5 addition, as leading candidate among the studied catalyst, decreased the activation energy to 83 kJmol -1 from 142 kJ/mol for pristine KSi. KSiH3 system with catalyst V2 O5 started desorbing at 100 °C and could achieve highest weight loss 3.7 wt % which is very close to theoretical value. No disproportionation phenomenon is detected which indicated that the reaction between KSiH3 and KSi is flawlessly reversible with a hydrogen storage capacity of 3.7 wt % H2 . The XPS investigation suggested a partial reduction of +5 oxidation state (corresponding to V2 O5 ) to metallic state, which is proposed as the possible cause of this improvement. Highlights: Activation energy of H2 desorption is lowest i.e. 83 kJ mol −1 for V2 O5 added KSiH3 . Onset H2 desorption temperature was reduced to 100 °C. XPS study suggested the reduction of V2 O5 to metallic V, which acted as catalyst.