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Tuning Hole Accumulation of Metal Oxides Promotes the Oxygen Evolution Rate
ACS Catalysis ( IF 12.9 ) Pub Date : 2020-08-20 , DOI: 10.1021/acscatal.0c02882
Peikun Zhang , Wei Wang 1 , Hui Wang 2 , Yanbo Li , Chunhua Cui
Affiliation  

Although much is known about the increased rate of a catalyst required for the oxygen evolution reaction (OER), the hole accumulation behaviors of the catalyst on both photo- and dark electrodes remain uncovered. We present a rational tuning of the hole-accumulation and hole-transfer ability of a catalyst by in situ deposition of IrOx on NiOx islands on model Si electrodes and we demonstrate a distinct hole accumulation behavior during the OER through electrochemical methods, in situ UV–vis and Raman spectroelectrochemistry. We find that the NiOx islands with <10% coverage on an n++-Si dark electrode demonstrate a 6-fold higher capacity of hole accumulation relative to that on an n-Si photoanode under illumination. A further in situ targeted deposition of soluble hexahydroxyiridate on the NiOx leads to the formation of NiOx/IrOx junctions, where the IrOx further depletes the extracted holes by NiOx from the n-Si photoanode decreasing the overpotential by ∼260 mV at 20 mA cm–2, yet the IrOx promotes the hole accumulation at the NiOx/IrOx on the dark electrodes presenting a similar decrease of the overpotential. In contrast to the dark-holes, an extremely lower charging level of photogenerated holes of the same catalyst at the identical current density reasoned a seemingly higher reactivity to drive the OER, and reasonably demonstrated a stronger oxidation/corrosion to the Si electrode.

中文翻译:

金属氧化物的微孔积累促进氧气释放速率

尽管对于氧释放反应(OER)所需的催化剂的增加速率知之甚少,但仍未发现该催化剂在光电极和暗电极上的空穴累积行为。我们通过在模型Si电极上的NiO x岛上原位沉积IrO x,提出了催化剂的空穴积累和空穴转移能力的合理调整,并且我们通过电化学方法证明了在OER期间原位的空穴积累行为。紫外可见光谱和拉曼光谱电化学。我们发现NiO xn ++-Si暗电极上的<10%覆盖率的孤岛表明,在光照下,其空穴累积能力是n-Si光电阳极的6倍。可溶性六羟基铱酸盐在NiO x上的进一步原位靶向沉积导致NiO x / IrO x结的形成,其中IrO x进一步耗尽了来自n-Si光阳极的NiO x提取的空穴,使过电势降低了约260 mV在20 mA cm –2时,IrO x会促进NiO x / IrO x处的空穴积累在暗电极上的过电位下降类似。与黑洞相反,在相同的电流密度下,相同催化剂的光生空穴的极低充电水平导致驱动OER的反应活性似乎更高,并合理地证明了对Si电极的更强的氧化/腐蚀。
更新日期:2020-09-20
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