Hong Zhang , Huanqiao Li , Xiaoming Zhang , Suli Wang , Gongquan Sun
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引用次数: 0
Abstract
Phosphoric acid (PA), utilized as an electrolyte in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), has been observed to exert a detrimental effect on oxygen reduction reaction (ORR) electrocatalyst, consequently compromising cell performance. To comprehensively elucidate the impact of phosphoric acid on ORR, this study employs a range of electrochemical techniques, including electrochemical impedance spectroscopy and voltammetry method. The negative influence of PA on commercial Pt/C electrocatalyst manifests differently under various potentials and PA concentrations. Upon the introduction of PA, the decay rate and amplitude of ECSA, as calculated by Hupd adatoms, are notably smaller compared to the kinetic current density generated by the oxygen reduction reaction. Particularly, in the kinetic-controlled potential range, the negative impact of PA becomes more pronounced at higher electrode potentials, accompanied by a significantly steeper Tafel slope. Additionally, the EIS results suggest that phosphoric acid may gradually transform into polyphosphoric acid at a high concentration, accentuating the poisoning effect of PA under steady-state conditions. However, a high PA concentration can substantially alter the electrolyte properties, potentially leading to an inaccurate assessment of PA tolerance in electrocatalysts. Hence, it is imperative to consider the appropriate PA concentration when evaluating PA tolerance and to discern the poisoning mechanism under different electrode potentials.
磷酸(PA)被用作高温聚合物电解质膜燃料电池(HT-PEMFCs)的电解质,据观察会对氧还原反应(ORR)电催化剂产生不利影响,从而损害电池性能。为了全面阐明磷酸对 ORR 的影响,本研究采用了一系列电化学技术,包括电化学阻抗光谱法和伏安法。在不同的电位和 PA 浓度下,PA 对商用 Pt/C 电催化剂的负面影响表现不同。引入 PA 后,与氧还原反应产生的动力学电流密度相比,由 Hupd adatoms 计算得出的 ECSA 衰减率和振幅明显变小。特别是在动力学控制的电位范围内,PA 的负面影响在电极电位较高时变得更加明显,同时伴随着明显陡峭的 Tafel 斜坡。此外,EIS 结果表明,高浓度磷酸可能会逐渐转化为多磷酸,从而加剧 PA 在稳态条件下的中毒效应。然而,高浓度 PA 会大大改变电解质的特性,从而可能导致对电催化剂耐受 PA 能力的评估不准确。因此,在评估 PA 耐受性时必须考虑适当的 PA 浓度,并辨别不同电极电位下的中毒机制。
期刊介绍:
Electrochimica Acta is an international journal. It is intended for the publication of both original work and reviews in the field of electrochemistry. Electrochemistry should be interpreted to mean any of the research fields covered by the Divisions of the International Society of Electrochemistry listed below, as well as emerging scientific domains covered by ISE New Topics Committee.