Carbon monoxide poisoning mitigation approaches for the anode of polymer electrolyte membrane fuel cells

Carbon monoxide (CO) poisoning mitigation is an important technological and fundamental challenge in the field of polymer electrolyte membrane fuel cells (PEMFC’s). The presence of CO even in very low concentrations (a few tens of ppm level) is the main source of overpotential loss in the anode of PEMFC’s. Therefore, the fundamental understanding of CO poisoning and providing mitigation approaches for this issue is of great interest. The possible approaches to solve the CO poisoning of PEM fuel cells can be categorized into two main technologies: on-fuel cell and off-fuel cell approaches. In this dissertation, a combination of electrochemical studies and numerical simulations are carried out to understand the mechanism of CO poisoning, and two different approaches are investigated to mitigate this issue: 1) Electrocatalysts with enhanced CO tolerance are studied; 2) An electrolytic selective CO removal system based on electrochemical water gas shift reaction is developed.DOCTOR OF PHILOSOPHY (MAE

A review of electrocatalysts with enhanced CO tolerance and stability for polymer electrolyte membarane fuel cells

A comprehensive review of the investigations performed in search for development of electrocatalysts with enhanced reformate tolerance for low temperature polymer electrolyte membrane (PEM) fuel cells are presented. Remarkable efforts have been made to attain improved catalytic activities and robustness by adding second element to Pt/C or third element to Pt–Ru/C, commercial catalysts for PEM fuel cell applications. The enhanced CO tolerance of the developed catalysts is strongly dependent on the type, composition and atomic ratios of the added elements/groups, and type and structure of the support materials. The synthesis method of the catalysts also plays a remarkable role in the catalytic activity and stability since it determines the structure, morphology and size distribution of the catalyst nanoparticles, which are directly effective on the stability and activity. Choosing a proper synthesis method, inclusion of appropriate content of suitable promoters to Pt-based catalysts, and using a proper support material are the major requirements of an effective catalyst. The CO tolerance enhancement has been attributed to the bi-functional mechanism and electronic effects. Understanding the underlying mechanisms and the activity–structure correlations will shed a light in designing novel electrocatalysts via innovative routes for excellent robust CO tolerant electrocatalysts

Paper-based membraneless hydrogen peroxide fuel cell prepared by micro-fabrication

A paper-based membraneless single-compartment hydrogen peroxide power source prepared by micro-electromechanical systems (MEMS) technology is reported. The cell utilizes hydrogen peroxide as both fuel and oxidant in a low volume cell fabricated on paper. The fabrication method used is a simple method where precise, small-sized patterns are produced which include the hydrophilic paper bounded by hydrophobic resin. Open circuit potentials of 0.61 V and 0.32 V are achieved for the cells fabricated with Prussian Blue as the cathode and aluminium/nickel as the anode materials, respectively. The power produced by the cells is 0.81 mW cm⁻² at 0.26 V and 0.38 mW cm⁻² at 0.14 V, respectively, even after the cell is bent or distorted. Such a fuel cell provides an easily fabricated, environmentally friendly, flexible and cost saving power source. The cell may be integrated within a self-sustained diagnostic system to provide the on-demand power for future bio-sensing applications.4 page(s

A membraneless hydrogen peroxide fuel cell using Prussian Blue as cathode material

This communication describes the exploitation of Prussian Blue, ferric ferrocyanide (Fe4III[FeII(CN)6]3), for the cathode side in a single-chamber membraneless fuel cell running on hydrogen peroxide (H2O2) as both fuel and oxidant. An open-circuit voltage (OCV) of 0.6 V has been obtained, which could be the highest OCV with H2O2 ever reported. The maximum power density was 1.55 mW cm−2 which showed a stable long-term operation in acidic media

The role of electronic properties of Pt and Pt alloys for enhanced reformate electro-oxidation in polymer electrolyte membrane fuel cells

One major challenge of PEM fuel cells development is to overcome the activity and durability issues of the current anode materials which are susceptible to hydrogen impurities. To design stable and efficient catalysts with enhanced reformate tolerance, a comprehensive understanding of the underlying mechanisms is crucial. In this work, the CO and CO2 tolerance of a series of Pt-based catalysts are tested in a PEM fuel cell. We report that the CO tolerance is the highest for PtMo/C followed by PtCoMo/C, PtRuMo/C, PtRuPb/C, PtRu/C, PtCo/C, PtFe/C, PtNi/C and Pt/C; while the CO2 tolerance increases in the order: PtCo, PtNi> PtRuPb> PtRu> PtCoMo> PtRuMo> PtFe> Pt> PtMo. In situ XAS measurements in combination with FEFF8 calculations are performed to correlate the CO and CO2 tolerance trends with the electronic properties of these Pt-based alloy catalysts. We find that the anode overpotential in the presence of CO2 can be generally related to the experimental Pt d-band vacancy or calculated d-band center, and thus governed by the Pt electronic properties modified by the alloyed metal(s). No such correlation is observed between the anode overpotential in the presence of CO and Pt electronic properties, which highlights the key roles of Mo or Ru in improving CO tolerance via promotion and bifunctional mechanisms. Building upon these results a new ternary alloy PtCoMo/C was synthesized. This electrocatalyst shows the best reformate tolerance in low temperature PEM fuel cells by taking advantage of the bifunctional mechanism induced by Mo and the ligand effect induced by Co simultaneously. Our findings put forward a theory which gives a strong perspective for further research and development of new inexpensive catalysts with superior CO tolerance and durability