Gong Luo, Koh Jiarui, Yeo Boon Siang
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
ChemSusChem. 2018 Nov 9;11(21):3790-3795. doi: 10.1002/cssc.201801639. Epub 2018 Oct 18.
A comprehensive study of the synergy between Fe and six transition metals (M=Ti, Co, Ni, Cu, Ag, Au), and how their M-Fe oxides electrocatalyze the oxygen evolution reaction (OER) was undertaken. Measurements were made using metal disks as the working electrodes and the addition of Fe ions to the 1 m KOH electrolyte. The surfaces of the metal disks were oxidized after the OER. Interestingly, Fe interacted synergistically with all metal oxide layers except for that of Ti, resulting in enhanced catalytic activity for the OER. At an overpotential (η) of 400 mV, the current densities of the Ni and Ag disks in the Fe ions-spiked electrolyte increased by 253 and 132 times, respectively, whereas it was only 20-30 times for the Co and Cu disks (compared with the OER in pure KOH at η=400 mV). The Tafel slopes of the Fe, Co, Ni, Cu, and Ag disks in 1 m KOH+Fe electrolyte were in the range of 29-42 mV dec . The surface morphology and post-OER concentration of Fe in the catalysts could not be used to account for differences in the OER activities. Cyclic voltammetry showed that improvements in the OER performance were accompanied by changes in the redox features of the metal disk electrodes, which indicated the presence of electronic interactions between them and the Fe . Strikingly, this was not observed between Ti and the Fe ions, which could explain the lack of synergy between Ti and Fe towards the OER catalysis. Electrochemical impedance spectroscopy indicated that the charge-transfer resistances of all the electrodes (except Ti) decreased after the addition of Fe ions. Fe plays an important role in all these observed phenomena and we propose that the surface-adsorbed Fe species serve as the main active sites for OER in these synergistic M-Fe combinations.
开展了一项关于铁与六种过渡金属（M = 钛、钴、镍、铜、银、金）之间协同作用以及它们的M - Fe氧化物如何电催化析氧反应（OER）的综合研究。使用金属圆盘作为工作电极，并向1 m KOH电解液中添加铁离子进行测量。在OER之后，金属圆盘的表面被氧化。有趣的是，铁与除钛之外的所有金属氧化物层都发生了协同作用，从而提高了对OER的催化活性。在400 mV的过电位（η）下，添加铁离子的电解液中镍和银圆盘的电流密度分别增加了253倍和132倍，而钴和铜圆盘的电流密度仅增加了20 - 30倍（与在η = 400 mV的纯KOH中进行的OER相比）。在1 m KOH + Fe电解液中，铁、钴、镍、铜和银圆盘的塔菲尔斜率在29 - 42 mV dec的范围内。催化剂中铁的表面形态和OER后浓度无法解释OER活性的差异。循环伏安法表明，OER性能的改善伴随着金属圆盘电极氧化还原特征的变化，这表明它们与铁之间存在电子相互作用。引人注目的是，在钛和铁离子之间未观察到这种情况，这可以解释钛和铁在OER催化方面缺乏协同作用的原因。电化学阻抗谱表明，添加铁离子后，所有电极（除钛外）的电荷转移电阻均降低。铁在所有这些观察到的现象中都起着重要作用，我们提出表面吸附的铁物种是这些协同M - Fe组合中OER的主要活性位点。
