A mechanistic study into the catalytic effect of Ni(OH)2 on hematite for photoelectrochemical water oxidation.
A mechanistic study into the catalytic effect of Ni(OH)2 on hematite for photoelectrochemical water oxidation.
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DOI：
10.1039/c3nr00569k
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发表时间：
2013-05
期刊：
影响因子：
6.7
通讯作者：
Gongming Wang;Yichuan Ling;Xihong Lu;Teng Zhai;Fang Qian;Y. Tong;Yat Li
中科院分区：
文献类型：
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作者：
Gongming Wang;Yichuan Ling;Xihong Lu;Teng Zhai;Fang Qian;Y. Tong;Yat Li
本文报道了Ni（OH）2对赤铁矿纳米线光电化学水氧化的催化作用机理研究。Ni化合物已被证明是电化学和光电化学水氧化的良好催化剂。虽然我们还观察到Ni催化剂修饰的赤铁矿光阳极的光电流改善，但我们发现光电流快速衰减，表明光电流不稳定。重要的是，我们揭示了增强的光电流是由于水氧化以及光致充电效应。除了氧化水之外，在赤铁矿中产生的光激发空穴有效地将Ni（2+）氧化成Ni（3+）（0.35V vs. Ag/AgCl）。光电流的不稳定性是由于Ni（2+）的耗尽所致。Ni（II）催化剂对水的催化氧化机理是一个两步过程，即Ni（2+）快速氧化为Ni（3+），然后Ni（3+）缓慢氧化为Ni（4+），Ni（4+）被认为是水氧化的活性催化物种。Ni（II）催化剂的催化效果受到Ni（4+）形成缓慢的限制。最后，通过抑制光生电荷效应，阐明了Ni（OH）2在赤铁矿表面光电化学水氧化反应中的真实的催化性能。这一工作为进一步研究镍基催化剂修饰光电极水氧化反应提供了重要参考。
We report a mechanistic study of the catalytic effect of Ni(OH)2 on hematite nanowires for photoelectrochemical water oxidation. Ni compounds have been shown to be good catalysts for electrochemical and photoelectrochemical water oxidation. While we also observed improved photocurrents for Ni-catalyst decorated hematite photoanodes, we found that the photocurrents decay rapidly, indicating the photocurrents were not stable. Importantly, we revealed that the enhanced photocurrent was due to water oxidation as well as the photo-induced charging effect. In addition to oxidizing water, the photoexcited holes generated in hematite efficiently oxidize Ni(2+) to Ni(3+) (0.35 V vs. Ag/AgCl). The instability of photocurrent was due to the depletion of Ni(2+). We proposed that the catalytic mechanism of the Ni(II) catalyst for water oxidation is a two-step process that involves the fast initial oxidation of Ni(2+) to Ni(3+), and followed by the slow oxidation of Ni(3+) to Ni(4+), which is believed to be the active catalytic species for water oxidation. The catalytic effect of the Ni(II) catalyst was limited by the slow formation of Ni(4+). Finally, we elucidated the real catalytic performance of Ni(OH)2 on hematite for photoelectrochemical water oxidation by suppressing the photo-induced charging effect. This work could provide important insights for future studies on Ni based catalyst modified photoelectrodes for water oxidation.