镍(氢)氧化物(NiOH)被认为是水的光电化学氧化的良好助催化剂,以及有机物在不同半导体上的光催化氧化。本文报道了高氯酸六胺镍(NiNH)大大提高了Bi2MoO6(BMO)的活性。在可见光下,苯酚在BMO上的氧化缓慢。在NiNH之后,NiOH,和Ni2+加载,苯酚氧化的最大速率分别增加了约16、8.8和4.7倍。使用BMO电极,所有催化剂均抑制O2还原,增强水(光)氧化,促进了固液界面的电荷转移,分别,其程度始终为NiNH>NiOH>Ni2+。固体发射光谱表明,所有催化剂都改善了BMO的电荷分离,其程度也随着NiNH>NiOH>Ni2+而变化。此外,在不含苯酚的NiNH/BMO水性悬浮液被辐照后,有相当多的Ni(III)物种,但一个微不足道的NH2自由基。因此,提出了一种合理的机制,涉及将Ni(II)空穴氧化为Ni(IV),对苯酚氧化有反应性,并因此促进O2还原。因为NH3是比H2O更强的配体,Ni(NH3)6的Ni(II)氧化比Ni(H2O)6容易。这项工作显示了如何通过助催化剂改善BMO光催化的简单途径。
Nickel (hydr)oxide (NiOH) is known to be good co-catalyst for the photoelectrochemical oxidation of water, and for the photocatalytic oxidation of organics on different semiconductors. Herein we report a greatly improved activity of Bi2MoO6 (BMO) by nickel hexammine perchlorate (NiNH). Under visible light, phenol oxidation on BMO was slow. After NiNH, NiOH, and Ni2+ loading, a maximum rate of phenol oxidation increased by factors of approximately 16, 8.8, and 4.7, respectively. With a BMO electrode, all catalysts inhibited O2 reduction, enhanced water (photo-)oxidation, and facilitated the charge transfer at solid-liquid interface, respectively, the degree of which was always NiNH > NiOH > Ni2+. Solid emission spectra indicated that all catalysts improved the charge separation of BMO, the degree of which also varied as NiNH > NiOH > Ni2+. Furthermore, after a phenol-free aqueous suspension of NiNH/BMO was irradiated, there was a considerable Ni(III) species, but a negligible NH2 radical. Accordingly, a plausible mechanism is proposed, involving the hole oxidation of Ni(II) into Ni(IV), which is reactive to phenol oxidation, and hence promotes O2 reduction. Because NH3 is a stronger ligand than H2O, the Ni(II) oxidation is easier for Ni(NH3)6+ than for Ni(H2O)6+. This work shows a simple route how to improve BMO photocatalysis through a co-catalyst.