Abstract

Herein, we report a special pulse potential method to increase methanol production and keep the Cu_xO/TiO₂ nanotube array (TNT) catalyst active during photoelectrocatalysis reduction of CO₂. The CuO/TNT catalyst was prepared via electrodeposition of copper on anodized titanium oxide followed by heat treatment. The variation of valence of copper in the photoelectrocatalytic reduction process was studied intensively by high-resolution transmission electron microscopy, XPS, and AES characterizations. Results show that the photocatalytically active CuO is apt to be reduced to elementary Cu during photoelectrocatalysis process, leading to rapid decay of photocatalytic activity. While for the case of pulse potential regime, another photocatalytically active oxide, Cu₂O, will be produced on the surface during anodic pulse, which can effectively maintain the photocatalytic activity of catalyst. CV study indicates that the oxidation of Cu is prior to the oxidation of methanol, so the methanol oxidation hardly ever happens during anodic pulse stage. The catalyst applied in pulse potential regime provided a much larger photocurrent than that in constant potential regime over an extended period of time. As a result, the yield of methanol produced in optimized pulse potential condition is greatly increased, nearly twice that in constant potential regime.

中文翻译：

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脉冲电势法在Cu x O / TNTs催化剂上高效，可持续地将CO 2转化为甲醇

摘要

本文中，我们报告了一种特殊的脉冲电势方法，该方法可提高甲醇产量并在光电催化还原CO _2的过程中保持Cu _x O / TiO ₂纳米管阵列（TNT）催化剂的活性。通过在阳极氧化的氧化钛上电沉积铜，然后进行热处理，制备了CuO / TNT催化剂。通过高分辨率透射电子显微镜，XPS和AES表征，深入研究了铜在光电催化还原过程中的价态变化。结果表明，在光电催化过程中，光催化活性CuO易于还原成元素铜，导致光催化活性迅速下降。对于脉冲电势情况，另一种光催化活性氧化物Cu ₂在阳极脉冲过程中会在表面产生O，可以有效维持催化剂的光催化活性。CV研究表明，Cu的氧化先于甲醇的氧化，因此在阳极脉冲阶段几乎不会发生甲醇的氧化。在延长的时间内，以脉冲电势方式施加的催化剂提供的光电流要比以恒定电势方式施加的催化剂大得多。结果，在优化的脉冲电势条件下产生的甲醇产率大大提高，几乎是恒定电势条件下的两倍。