【作者】 刘明俊；

【导师】 潘牧；

【作者基本信息】 武汉理工大学 ， 材料科学与工程， 2023， 硕士

【摘要】 质子交换膜燃料电池(Polymer exchange membrane fuel cells,PEMFCs)在提高燃料效率和减少碳排放方面具有广阔的应用前景。如今,质子交换膜燃料电池应用偏向重载交通工具,对耐久性的要求更高,要求在0.8 V以上的工作电位下长时运行,寿命要超过25000小时。工作电压的提高会加速电池材料的腐蚀,尤其是阴极催化层中的Pt和碳。目前已有研究表明催化层中Pt会促进碳载体的腐蚀,但0.8 V的运行工作电位正好是Pt的氧化电位区间,在此运行电位区间下,Pt成分对碳腐蚀的作用机理存在争议,一部分认为活性Pt比氧化Pt对碳腐蚀作用更强,一部分则持相反观点,本论文针对活性Pt和氧化Pt对碳腐蚀的影响规律展开研究:(1)在0.8 V恒电位运行工况下,催化层Pt会促进碳载体的腐蚀,含Pt电极初始碳腐蚀速率甚至是纯碳电极的27倍,即使后期达到稳态,含Pt电极的碳腐蚀速率也是纯碳电极的3倍;含Pt电极在恒电位运行工况下的碳腐蚀累积量变化规律可以分为三个阶段,第一段呈对数增长,第二阶段混合增长区,第三阶段呈线性增长;(2)设计了阶跃运行工况,在0.8 V恒电位运行工况中引入0.4 V恒电位运行控制Pt氧化物累积量,设置了高低两种阶跃频率,引入低电位阶跃可降低运行过程中Pt表面的氧化物累积量,并且阶跃频率越高,氧化物累积量越低。在恒电位运行60 min内,高频阶跃运行工况较恒电位运行工况的氧化物累积量降低了11.56%;(3)在运行6000 min后,高频阶跃运行工况造成的碳排放量甚至是恒电位运行工况的1.8倍,高频阶跃运行工况中Pt氧化物累积量的降低造成了15.55%的碳载体质量损失,是恒电位运行工况的2倍;表明活性Pt比Pt氧化物更容易促进碳的腐蚀;(4)高频阶跃运行工况在60 min内就造成了41.17%的电化学活性面积损失,是恒电位运行工况电化学活性面积损失量(17.88%)的2.3倍;三种运行工况在6000 min内,电极表面接触角达到平衡,这可能是因为碳表面官能团已经反应完全,碳和碳氧化物的转换达到稳态。更多还原

【Abstract】 Proton exchange membrane fuel cells(PEMFCs)has broad application prospects in improving fuel efficiency and reducing carbon emissions.Nowadays,the application of PEMFCs is biased towards heavy-duty vehicles which demands a higher durability.It requires that the PEMFCs should work at a working potential above 0.8 V span of more than 25,000 hours.The increase of working voltage will accelerate the corrosion of the cell materials,especially Pt and carbon in the cathode catalyst layer.At present,many researches have shown that Pt in the catalyst layer will promote the corrosion of carbon support,but the operating potential of 0.8 V is the oxidation potential range of Pt.In this operating potential range,the mechanism of Pt composition on carbon corrosion is controversial.Some believe that active Pt has stronger corrosion effect on carbon than oxidized Pt,while some hold the opposite view.In this paper,the influence of active Pt and oxidized Pt on carbon corrosion is studied:(1)At a constant potential of 0.8 V,the Pt will promote the corrosion of the carbon support.The initial carbon corrosion rate of the Pt-containing electrode is even 27 times that of the pure carbon electrode.Even if the steady state is reached in the later stage,the carbon corrosion rate of the Pt-containing electrode is 3 times that of the pure carbon electrode.The variation of carbon corrosion accumulation of Pt-containing electrode can be divided into three stages.The first stage is logarithmic growth,the third stage is linear growth,and the second stage is mixed growth zone.(2)The step operation procedure is designed.The 0.4 V constant potential operation is introduced to control the Pt oxide accumulation in the 0.8 V constant potential operation condition.The high and low step frequencies are set.The introduction of low potential step can reduce the oxide accumulation on the Pt surface during operation.The higher the step frequency,the lower the oxide accumulation.Within 60 min of constant potential operation,the oxide accumulation of high frequency step operation condition is 11.56 % lower than that of constant potential operation condition.(3)After 6000 min of operation,the carbon emission caused by the high-frequency step operation condition is 1.8 times that of the constant potential operation condition.The decrease of Pt oxide accumulation in the high-frequency step operation condition causes 15.55 % mass loss of carbon carrier,which is 2 times that of the constant potential operation condition.It shows that active Pt is easier to promote carbon corrosion than Pt oxide.(4)The high-frequency step operation condition caused 41.17 % of the electrochemical active area(ECSA)within 60 min,which was 2.3 times the loss of electrochemical active area(17.88 %)under the constant potential operation condition.The contact angle of the electrode surface reaches equilibrium within 60 min under the three operating conditions.This may be because the functional groups on the carbon surface have reacted completely,and the conversion of carbon and carbon oxides reaches a steady state.更多还原