Cell Reversal Tolerance

Ralph TR, Hudson S, Wilkinson DP (2006) Electrocatalyst stability in PEMFCs and the role of fuel starvation and cell reversal tolerant anodes. ECS Trans 1 67-84... 

Figure 17.10 shows the performance in Ballard stack hardware of three different cell-reversal-tolerant electrocatalysts prepared by Johnson Matthey. In this case the MEAs have received significant prior cell-reversal periods to drive the anodes to the limit of their tolerance. The impact that inclusion of a water electrolysis electrocatalyst has on the ability of the anode to sustain water electrolysis is evident. At the standard 40 wt% Pt, 20 wt% Ru/Shawinigan carbon black-based anode, the water electrolysis plateau is so short that it is difficult to detect. Only by using a cell reversal-tolerant electrocatalyst in the anode water electrolysis are plateaus evident in Figure 17.10. As a result, the degree of carbon corrosion is significantly reduced by the cell-reversal-tolerant electrocatalysts. The...

Improved MEA design will favor the oxidation of water over the carbon support. This can be accomplished through the approaches described below. For the results described, the cell reversal tolerance is the time to complete cell failure (defined as a cell voltage of -2 V) during a simulated fuel starvation experiment. 

S. Ye, Fuel cell anode structure for voltage reversal tolerance, US Patent 7608358, assigned to BDF IP Holdings Ltd. (Vancouber, BC, CA), October 27, 2009. 

Knights S etal, 2001a, Fuel Cell Anode Structure for Voltage Reversal Tolerance. WO 01/15247. 

Efficient Oxygen Evolution Reaction Catalysts for Cell Reversal and Start/Stop Tolerance... 

Ye S (2008) Reversal-tolerant catalyst layers, hi Zhang J (ed) PEM fuel cell electrocatalysts and catalyst layers fundamentals and application. Springer, London... 

In addition to enhancing the presence of water at the anode through modifications to the anode structure, a PEM fitel cell can be made more tolerant to voltage reversal by incorporating an additional catalyst, a water electrolysis (oxygen evolution reaction, OER) catalyst, at the anode to promote the electrolysis of water [14-16, 18]. In this way, more of the current forced through the cell may be consumed by the electrolysis of water than by the oxidation of the anode components. In a reversal-tolerant fuel cell, the anode comprises a first catalyst composition for evolving protons from the fuel and a second catalyst composition for water electrolysis. 

To improve voltage reversal tolerance of PEM fuel cells, water electrolysis catalysts have been incorporated into anode stractures by Johnson Matthey and Ballard Power Systems [12-17]. In such a reversal-tolerant fuel cell, the anode comprises a first catalyst composition for evolving protons from the fuel and a second catalyst composition for water electrolysis. 

The use of reversal-tolerant eells has signifieant benefits for PEM fuel cell technology development ... 

Ye S, Beattie P, Campbell SA, Wilkinson DP. Anode catalyst compositions for a voltage reversal tolerant fuel cell. US Patent Appl 2004/0013935. 

Barton RH. Cell voltage monitor for a fuel cell stack. US Patent 6724194. 2004. Knights SD, Taylor JL, Wilkinson DP, Wainwright DS. Fuel cell anode structures for voltage reversal tolerance. US Patent 6517962. 2003. 

Knights S D, Wilkinson D P, Campbell S A, Taylor J L, Gascoyne J M and Ralph, T R (2005a), Solid Polymer Fuel Cell -with Improved Voltage Reversal Tolerance, US patent 6,936,370,Aug 30,2005. 

Knights S D, Taylor J L, Wilkinson D P and Campbell S A (2001), Supported Catalysts for the Anode of a Voltage Reversal Tolerant Fuel Cell. PCT WO 01/15254 A2, 01 March 2001. 

Cell can tolerate overcharge and reversal Hj pressure gives an indication of state of charge... 

In a mouse model for autoimmune non-obese diabetes (NOD), the full-blown diabetes could be reversed to normoglycaemia by treatment with CD3 antibodies. In these diabetes- tolerant mice, the proportions of CD4+ CD25+ regulatory T cells were increased. Moreover, the CD4+ CD25+ regulatory T cells of the tolerant mice produced high levels of... 

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