Development and understanding of Pt-based catalysts supported on transition metal carbides for polymer electrolyte fuel cells

Monzó Giménez, Javier (2019). Development and understanding of Pt-based catalysts supported on transition metal carbides for polymer electrolyte fuel cells. University of Birmingham. Ph.D.

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Abstract

The consumption of energy has increased in the last decades due to the industrial development and to a population growth. Consequently, the emissions of gases responsible for the Greenhouse effect are increasing and thus the Global temperature as well. For this reason, our society is pushing to find alternative energy generators. Polymer electrolyte fuel cells (PEFC) are emerging as a potential candidate to replace common energy generators due to its special features. The wide commercialization of Polymer electrolyte fuel cell technology is limited for some factors as the cost and durability of the device. The cost of PEFC is high because Pt is used as the catalysts. Also, the degradation of the catalyst at operation conditions leading in a failure of the device is another limiting factor. For that reason, the development of alternative materials is the key for a wide commercialization of PEFC. In order to develop novel catalysts, a novel methodology to understand the degradation mechanism has been developed, combining cyclic voltammetry and X-ray fluorescence (XRF). For the validation of the methodology, unsupported Pt nanoparticles and Pt nanoparticles supported on TaC (Pt/TaC) were used. Pt/TaC showed a mass activity improvement and a considerable stability. On the basis of these results, a series of transition metal carbides (TMC) with high surface area were synthesised: VC, NbC and TaC. Pt nanoparticles were dispersed on the TMC (Pt/TMC) and the resulting catalysts were physically characterized. Also, the stability and mass activity of the Pt/TMC catalysts was assessed. Pt/NbC was the most stable catalyst under oxidative conditions and it presented an improvement of the mass activity. In order to tackle the other problem of the PEFC, Pt-alloys with transition metal have been studied for reducing the cost. PtCo nanoparticles were synthesised and characterized and then they were dispersed on NbC. The resulting catalyst, PtCo/NbC was characterized and its stability was tested. PtCo/NbC was more durable and catalytically active than the commercial Pt/C catalysts.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):