Toward Understanding the Utilization of Oxygen Reduction Electrocatalysts under High Mass Transport Conditions and High Overpotentials
Toward Understanding the Utilization of Oxygen Reduction Electrocatalysts under High Mass Transport Conditions and High Overpotentials
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DOI：
10.1021/acscatal.1c03908
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发表时间：
2021-12-14
期刊：
影响因子：
12.9
通讯作者：
Kucernak, Anthony R. J.
中科院分区：
文献类型：
--
作者：
Jackson, Colleen;Lin, Xiaoqian;Kucernak, Anthony R. J.
目前，使用旋转圆盘电极（RDE）测量的高电催化剂氧还原反应（ORR）性能与原位膜电极组件（MEA）性能之间存在脱节。电催化剂性能的脱节引发了关于RDE技术在将性能外推到更高过电位时的陷阱以及如何提高原位催化剂层性能以满足雄心勃勃的燃料电池目标的问题。这项工作旨在通过使用浮动电极（FE）技术测量高质量传输条件下高过电位下ORR的非原位性能来弥补这一差距。这里,我们确定的性能三个Pt / C electrocatalysts使用1米高氯酸和1米的铁硫酸表明MEA活动以80度C, 150 kPa (g)大大低于室温和常压下性能相同的催化剂在使用RDE 1米高氯酸和有限元方法,也低于1米的铁硫酸,暗示意味着限制并不纯粹由于磺酸盐电解质吸附。最后，对FE和MEA数据进行建模，得到FE（无氧化物条件）下的j(o)值为11-26 μ A cm(-2)，是MEA测量值的4-6倍。这种差异被解释为由于FE系统中更好的除水。这项工作表明，由于水输送不良，MEA催化剂层未得到充分利用，在0.65 V下，400 μ g(Pt) cm(-2) （25-40 A mg(-1)）的电流密度相当于10-16 A cm(-2)，而MEA的电流质量活性为
There is currently a disconnect between the high electrocatalyst oxygen reduction reaction (ORR) performance measured ex situ, using the rotating disc electrode (RDE), and the in situ membrane electrode assembly (MEA) performance. The disconnect in the electrocatalyst performance raises questions both about the pitfalls of the RDE technique at extrapolating the performance to higher overpotentials and how to improve the in situ catalyst layer performance to meet ambitious fuel cell targets. This work aims to bridge the gap by measuring the ORR ex situ performance under high mass transport conditions, at high overpotentials, using the floating electrode (FE) technique. Here, we determine the performance of three Pt/C electrocatalysts using the FE in 1 M HClO4 and 1 M H2SO4 to show that the MEA activities measured at 80 degrees C, 150 kPa(g) were substantially lower than the room temperature and pressure performance of the same catalyst in 1 M HClO4 using the RDE and FE methods and also lower than the FE in 1 M H2SO4, implying MEA limitations are not purely due to sulfonate adsorption from the Nafion. Finally, FE and MEA data was modeled which obtained j(o) values on the FE (oxide free conditions) which were 4-6x larger, at 11-26 mu A cm(-2), than those measured on the MEA. The difference is interpreted as due to better water removal in the FE system. This work shows that MEA catalyst layers are vastly underutilized, due to poor water transport, and current densities equivalent to 10-16 A cm(-2) at 0.65 V for 400 mu g(Pt) cm(-2) (25-40 A mg(-1)) are achievable, whereas the current mass activity of MEAs is