THESIS
2018
xix, 163 pages : illustrations (some color) ; 30 cm
Abstract
Hydrogen is a clean energy carrier that has all criteria considered for an alternative energy source. One of promising ways to store intermittent and renewable energy sources is producing hydrogen by water splitting. One of the main issues in water splitting is the requirement of highly cost electrocatalysts such as Pt for hydrogen evolution reaction (HER). The development of cost-effective, sustainable and efficient catalysts for HER is of significance.
To reach this goal, various types of materials were explored in this work including the transition metal and nitrogen co-doped composites (Co-N-C), Fe
3C encapsulated in N-doped carbon nanotubes (Fe
3C@NCNT), Co nanoparticles encapsulated in N-doped electrospun carbon nanofibers (Co-PAN) as well as the Pd-based catalysts. Their catalytic...[
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Hydrogen is a clean energy carrier that has all criteria considered for an alternative energy source. One of promising ways to store intermittent and renewable energy sources is producing hydrogen by water splitting. One of the main issues in water splitting is the requirement of highly cost electrocatalysts such as Pt for hydrogen evolution reaction (HER). The development of cost-effective, sustainable and efficient catalysts for HER is of significance.
To reach this goal, various types of materials were explored in this work including the transition metal and nitrogen co-doped composites (Co-N-C), Fe
3C encapsulated in N-doped carbon nanotubes (Fe
3C@NCNT), Co nanoparticles encapsulated in N-doped electrospun carbon nanofibers (Co-PAN) as well as the Pd-based catalysts. Their catalytic activities for HER were evaluated and compared with the commercial Pt/C catalyst. All these materials were very active for HER in both acidic and alkaline solutions. The overpotential at current density of 10 mA cm
-2 for noble metal-free catalysts were 235 mV for Co-N-C, 154 mV for Fe
3C@NCNT and 159 mV for Co-PAN which were lower than most of non-precious metal based- and metal free catalysts. According to our DFT calculation results, the transition metal and N-doped carbon played important roles in improving their catalytic activities. Specifically, the active sites for Co-N-C could be related to Me/N/C moieties. The synergistic effect between the Fe
3C and N-doped CNTs is the main reason for improving its catalytic activity by weakening the H adsorption energy. The Pd
3Ru alloy thermal annealed at 300˚C showed excellent catalytic activity for HER that was even higher than Pt in alkaline solutions. This makes PdRu alloys a potential substitution for Pt. DFT calculation results indicated that the hydrogen binding energy on Pd
3Ru alloy was weaker than Pd. This work gives guidance to develop more efficient and cost-effective catalysts for HER, as well as other reactions.
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