Examination of electrocatalysis in the anodic O2 evolution reaction at Pt through evaluation of the adsorption behaviour of kinetically involved intermediate states

B. Conway, T. Liu
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引用次数: 7

Abstract

In regular heterogeneous catalytic reactions, evaluation of the adsorption behaviour of the ephemeral intermediates that participate kinetically in the main reaction pathway is often inaccessible experimentally. In electrocatalysis, on the other hand, electrochemical transient methods can provide such information. In the present paper, potential-relaxation transients are used to derive information on the electroactive, kinetically significant adsorbed intermediate states that are involved in the anodic O2 evolution reaction (OER) at Pt electrodes. By means of such transients, digitally recorded over 5–6 decades of time from microseconds to seconds, the adsorption capacitance of the intermediate states in the reaction is evaluated as a function of potential over a range corresponding to appreciable current densities for O2 evolution. Anodic O2 evolution takes place at Pt, as at all other metal anodes, on an oxide film. A well-defined state of such a film must be established by a pre-conditioning programme to make meaningful and reproducible kinetic studies on the OER. The state of the oxide film is conveniently characterized by means of cyclic-voltammetry. The intermediate surface states in the reaction can be two or more oxidation states of Pt atoms in the oxide and OH or O species at the oxide’s surface. Two distinct types of adsorption behaviour are distinguished for potentials above and below ca. 1.85 V against the reversible H2 electrode (RHE), and are related to the observed kinetics of the OER.
通过评价动力学参与中间态的吸附行为来考察Pt阳极析氧反应中的电催化作用
在常规的非均相催化反应中,对主要反应途径中动态参与的短暂中间体的吸附行为的评价通常无法通过实验进行。另一方面,在电催化中,电化学瞬态方法可以提供这样的信息。在本论文中,电位弛豫瞬态被用来推导Pt电极上参与阳极氧析出反应(OER)的电活性、动力学意义显著的吸附中间态的信息。通过这样的瞬态,数字记录在5-6年的时间内,从微秒到秒,反应中中间状态的吸附电容被评估为电位的函数,其范围对应于O2演化的可感知电流密度。氧化膜上的铂和其他金属阳极一样,发生阳极氧析出。为了对OER进行有意义和可重复的动力学研究,必须通过预处理程序建立这种薄膜的明确状态。氧化膜的状态可以用循环伏安法方便地表征。反应中的中间表面态可以是氧化物中的Pt原子和氧化物表面的OH或O两种或两种以上的氧化态。两种不同类型的吸附行为被区分为电位高于和低于约1.85 V的可逆H2电极(RHE),并与观察到的动力学OER有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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