DETERMINATION OF THE ADSORPTION BEHAVIOR OF OVERPOTENTIAL-DEPOSITED HYDROGEN-ATOM SPECIES IN THE CATHODIC HYDROGEN-EVOLUTION REACTION BY ANALYSIS OF POTENTIAL-RELAXATION TRANSIENTS
DETERMINATION OF THE ADSORPTION BEHAVIOR OF OVERPOTENTIAL-DEPOSITED HYDROGEN-ATOM SPECIES IN THE CATHODIC HYDROGEN-EVOLUTION REACTION BY ANALYSIS OF POTENTIAL-RELAXATION TRANSIENTS
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DOI：
10.1039/f19858101841
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发表时间：
1985-01-01
期刊：
影响因子：
--
通讯作者：
BAI, L
中科院分区：
文献类型：
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作者：
CONWAY, BE;BAI, L
尽管它在电催化和电极过程的机理方面具有重要意义，但迄今为止，在可观的法拉第电流下进行的电极反应中，对动力学相关中间体（例如H2演化中的H）的吸附行为的实验测定仍然很少发展。一种新的分析极化电流中断后开路过电位衰减动力学的方法，已被应用于研究过电位沉积（o.p.d）的吸附行为。氢在可观电流下作为H2阴极演化的中间产物产生。描述了Ni和电沉积Ni - mo - cd复合正极材料的研究结果。该方法首次能够可靠地确定H覆盖率作为电位的函数，在明显的过电位下，并且可以直接准确地评估连续法拉第反应中o.p.d.物种的相应吸附伪电容行为。结果表明，在过电位为-0.15 ~ -0.25 V时，这些金属表面的H覆盖达到极限值，因此，在这些金属表面，H2的法拉第过程在不完全但明显被H原子覆盖的表面进行。通过对放电和电化学解吸机制的稳态分析，从理论上解释了这种行为，并评估了解释所观察到的h吸附行为所需的速率常数的比率。根据观察到的h吸附行为和反应机理的步骤，讨论了所研究金属上h2 -析出反应的Tafel斜率。
Despite its major importance in electrocatalysis and mechanistic aspects of electrode processes, the experimental determination of the adsorption behaviour of kinetically involved intermediates, e.g. H in H2 evolution, in electrode reactions proceeding at appreciable Faradaic currents has hitherto remained little developed. A new method of analysis of the kinetics of the decay of overpotential on open-circuit, following interruption of a polarizing current, has been applied to the study of the adsorption behaviour of the ‘overpotential-deposited’(o.p.d.) H generated as an intermediate in the cathodic evolution of H2 at appreciable currents. Results are described for Ni and electrodeposited Ni–Mo–Cd composite cathode materials.The method enables, for the first time, the H coverage to be reliably determined as a function of potential, at appreciable overpotentials, and the corresponding adsorption pseudocapacitance behaviour to be directly and accurately evaluated for the o.p.d. species in a continuous Faradaic reaction. The results show that H coverage at the surfaces of these metals attains limiting values at overpotentials of –0.15 to –0.25 V, so that the Faradaic process of H2 evolution proceeds, at these metals, on a surface incompletely but appreciably covered by H atoms. By application of a steady-state analysis to a discharge and electrochemical-desorption mechanism this behaviour is explained theoretically and the ratios of rate constants required to account for the observed H-adsorption behaviour are evaluated. The Tafel slopes for the H2-evolution reaction at the metals studied are discussed in terms of the observed H-adsorption behaviour and steps in the reaction mechanism.