Shrinking the Hydrogen Overpotential of Cu by 1 V and Imparting Ultralow Charge Transfer Resistance for Enhanced H2 Evolution
Shrinking the Hydrogen Overpotential of Cu by 1 V and Imparting Ultralow Charge Transfer Resistance for Enhanced H2 Evolution
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DOI：
10.1021/acscatal.8b01172
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发表时间：
2018-07-01
期刊：
影响因子：
12.9
通讯作者：
Kundu, Subrata
中科院分区：
文献类型：
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作者：
Anantharaj, Sengeni;Amarnath, Thangavel S.;Kundu, Subrata
铜及其氧化物是将CO2电化学转化为增值小有机物的最佳电催化剂之一，因为其高的氢过电压，使得析氢反应（HER）成为不良副反应。在这里，我们报告了一个有趣的发现，把表面氧化铜的性质颠倒在电化学H-2进化。众所周知，金属离子的电化学反应性对电解质中与其配位的阴离子高度敏感。在Cu的情况下，当其为氧化铜形式时，氢过电压是巨大的。尽管如此，我们发现，当Cu与Se 2-离子配位为Cu 2Se时，氢过电压缩小了类似于1V，赋予超低的电荷转移电阻（R-CT），其根据进行硒化的方式从0.32 Ω变化到0.61 Ω。用两种不同的方法进行硒化。在一种方法中，采用常规搅拌在90 ℃下在预热的NaHSe溶液中硒化Cu泡沫20 min。在另一种方法中，采用水热处理在120 ℃下用NaHSe溶液硒化Cu泡沫1 h。湿化学法在泡沫铜上制备了蜂窝状的Cu 2Se片层（命名为Cu 2Se-ch/Cu），水热法制备了均匀的Cu 2Se棒状结构（命名为Cu 2Se-ht/Cu）。在0.5 M H2SO 4中进行的HER电催化研究表明，Cu 2Se-ch/Cu和Cu 2Se-ht/Cu具有相似的动力学，Tafel斜率为32至35 mV dec（-1），这更接近最先进的Pt/C。有趣的是，当极化至高达-0.85V（相对于RHE）时，Cu 2Se-ch/Cu递送-1200mA cm（-2）的总动力学电流密度，而Cu 2Se-ht/Cu仅递送-780mA cm（-2）的最大值。
Copper and its oxides are among the best electrocatalysts for the electrochemical conversion of CO2 to value-added small organics because of its high hydrogen overvoltage, making the hydrogen evolution reaction (HER) a poor side reaction. Here we report an interesting finding that turned the nature of surface-oxidized Cu upside down in electrochemical H-2 evolution. It is commonly known that the electrochemical reactivity of a metal ion is highly sensitive to the anion to which it is coordinated in the electrolyte. In the case of Cu, when it is in the form of copper oxide, the hydrogen overvoltage is huge. Nonetheless, we found that when Cu is in coordination with Se2- ions as Cu2Se, the hydrogen overvoltage was shrunken by similar to 1 V, imparting ultralow charge transfer resistance (R-CT) that varied from 0.32 to 0.61 Omega depending on the means by which selenization was carried out. Selenization was done by two different methods. In one method, conventional stirring was employed to selenize Cu foam in a preheated NaHSe solution at 90 degrees C for 20 min. In another method, hydrothermal treatment was employed to selenize Cu foam with NaHSe solution at 120 degrees C for 1 h. The wet chemical method yielded honeycomb-like hierarchical arrays of Cu2Se sheets on Cu foam (designated as Cu2Se-ch/Cu), and the hydrothermal method yielded a uniform array of spiky rods of Cu2Se (designated as Cu2Se-ht/Cu). The HER electrocatalytic studies carried out in 0.5 M H2SO4 showed that Cu2Se-ch/Cu and Cu2Se-ht/Cu had similar kinetics, with Tafel slopes of 32 to 35 mV dec(-1), which is closer to the state-of-the-art Pt/C. Interestingly, the Cu2Se-ch/Cu delivered a total kinetic current density of -1200 mA cm(-2) when polarized up to -0.85 V vs RHE, whereas Cu2Se-ht/Cu delivered a maximum of -780 mA cm(-2) only.