Surface Composition of n‐GaAs Cathodes during Hydrogen Evolution Characterized by In Situ Ultraviolet‐Visible Ellipsometry and In Situ Infrared Spectroscopy
Surface Composition of n‐GaAs Cathodes during Hydrogen Evolution Characterized by In Situ Ultraviolet‐Visible Ellipsometry and In Situ Infrared Spectroscopy
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原位紫外-可见椭圆光度法和原位红外光谱表征析氢过程中 n-GaAs 阴极的表面成分
DOI：
10.1149/1.1838283
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发表时间：
1998
影响因子：
3.9
通讯作者：
J. Chazalviel
中科院分区：
文献类型：
--
作者：
B. Erné;M. Stchakovsky;F. Ozanam;J. Chazalviel
首次用原位光谱技术研究了(100)n-GaAs电极在酸性水溶液中阴极析氢过程中的化学成分。在发生析氢的整个电势范围内观察到了砷化镓的阴极分解，根据电势的不同，分解产物是Ga(Aq)3+或Ga(S)0和As(S)0或As3(G)。原位紫外可见椭偏测量仪明确地表明，在足够负的电位下，表面被金属镓部分覆盖。示差模式下的原位红外光谱表明，在氢析出时，氢总是与砷原子结合，而不是与镓原子结合。亚单分子层的氢覆盖率与外加电势近似成线性关系，并且在外加电势循环时表现出滞后。氢表面覆盖率、电流密度和外加电势之间的关系给出了直接的新证据，即增加砷化镓电极的氢表面覆盖率会导致平带电位的负移。氢表面复盖率对外加电势变化的时间响应的测量提供了第一个直接证据，证明氢的演化遵循Volmer-Heyrovsky路线。
The chemical composition of (100) n-GaAs electrode surfaces has been studied for the first time during cathodic hydrogen evolution in acidic aqueous solutions by in situ spectroscopic techniques. Cathodic decomposition of GaAs is observed in the entire potential range where hydrogen evolution occurs, decomposition products being Ga (aq) 3+ or Ga (s) 0 and As (s) 0 or AsH 3(g) , depending on the potential. In situ UV-visible ellipsometry shows unambiguously that the surface is partially covered by metallic gallium at sufficiently negative potentials. In situ infrared spectroscopy in the differential mode reveals that when hydrogen evolution occurs, hydrogen always binds to arsenic atoms, not to gallium atoms. The submonolayer hydrogen coverage is approximately linear with the applied potential and shows hysteresis upon cycling of the applied potential. A correlation between hydrogen surface coverage, current density, and applied potential gives direct new evidence that an increase in the hydrogen surface coverage of GaAs electrodes causes a negative shift of the flatband potential. Measurements of the time response of hydrogen surface coverage to changes of the applied potential provide the first direct evidence that hydrogen evolution follows a Volmer-Heyrovsky route.