Electrochemical Generation of a Hydrogen Bubble at a Recessed Platinum Nanopore Electrode
Electrochemical Generation of a Hydrogen Bubble at a Recessed Platinum Nanopore Electrode
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DOI：
10.1021/acs.langmuir.5b00234
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发表时间：
2015-04-21
期刊：
影响因子：
3.9
通讯作者：
White, Henry S.
中科院分区：
文献类型：
--
作者：
Chen, Qianjin;Luo, Long;White, Henry S.
我们报道了在凹入的铂纳米孔电极的空腔内产生单个氢气泡的电化学过程。凹入式铂电极是玻璃中的一个圆锥孔，它在纳米孔底部包含一个微米级的铂盘(半径为1-10微米)和一个纳米级的孔口(半径为10-100 nm)，该孔限制了电活性分子和溶解气体在纳米孔腔和整体溶液之间的扩散。在伏安实验中，在铂盘电极上形成了H-2气泡，这是由于H+在0.25M的H_2SO_4溶液中还原的结果；在伏安响应中，由于气泡在纳米孔洞内的快速形核和长大，导致阴极电流急剧下降，从而表明了液-气相转变。对纳米孔腔内溶解H-2浓度分布的有限元模拟表明，当临界过饱和浓度接近0.22M时，氢气泡在凹陷的铂电极表面发生形核，这与以前在(非凹陷的)铂圆盘电极(类似于0.25M)上得到的值一致。由于纳米孔口限制了H-2从纳米孔腔扩散出去，因此在反向伏安扫描上很容易观察到与陷落在凹腔中的气体和溶解的H-2的氧化相对应的阳极峰。在高扫描速率下，与H-2氧化峰相关的电荷积分接近于H+还原峰的电荷积分，证实了阳极峰对H-2氧化的指认。在凹槽纳米孔电极上由水氧化产生O-2气泡的初步结果与电产生H-2气泡的结果一致。
We report the eleetrochemical generation of a single hydrogen bubble within the cavity of a recessed Pt nanopore electrode. The recessed Pt electrode is a conical pore in glass that contains a micrometer-scale Pt disk (1-10 mu m radius) at the nanopore base and a nanometer-scale orifice (10-100 nm radius) that restricts diffusion of electroactive molecules and dissolved gas between the nanopore cavity and bulk solution. The formation of a H-2 bubble at the Pt disk electrode in voltammetric experiments results from the reduction of H+ in a 0.25 M H2SO4 solution; the liquid-togas phase transformation is indicated in the voltammetric response by a precipitous decrease in the cathodic current due to rapid bubble nucleation and growth within the nanopore cavity. Finite element simulations of the concentration distribution of dissolved H-2 within the nanopore cavity, as a function of the H+ reduction current, indicate that H-2 bubble nucleation at the recessed Pt electrode surface occurs at a critical supersaturation concentration of similar to 0.22 M, in agreement with the value previously obtained at (nonrecessed) Pt disk electrodes (similar to 0.25 M). Because the nanopore orifice limits the diffusion of H-2, out of the nanopore cavity, an anodic peak corresponding to the oxidation of gaseous and dissolved H-2 trapped in the recessed cavity is readily observed on the reverse voltammetric scan. Integration of the charge associated with the H-2 oxidation peak is found to approach that of the H+ reduction peak at high scan rates, confirming the assignment of the anodic peak to H-2 oxidation. Preliminary results for the electrochemical generation of O-2 bubbles from water oxidation at a recessed nanopore electrode are consistent with the electrogeneration of H-2 bubbles.