Effects of bubbles on the electrochemical behavior of hydrogen-evolving Si microwire arrays oriented against gravity
Effects of bubbles on the electrochemical behavior of hydrogen-evolving Si microwire arrays oriented against gravity
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DOI：
10.1039/d0ee00356e
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发表时间：
2020-06-01
影响因子：
32.5
通讯作者：
Lewis, Nathan S.
中科院分区：
文献类型：
--
作者：
Kempler, Paul A.;Coridan, Robert H.;Lewis, Nathan S.
在0.50 M H2SO 4（aq）溶液中进行析氢反应，测量了平面和微丝阵列镀铂n（+）-Si阴极的H（2）气泡膜的尺寸分布、覆盖率、电化学阻抗和传质性质。倒置的平面n（+）-Si/Ti/Pt阴极产生大的、静止的气泡，这导致欧姆电位降的显著增加。相比之下，无论取向如何，微丝阵列n（+）-Si/Ti/Pt阴极在表面上表现出较小的气泡层，并且气泡的形成基本上不增加H-2（g）产生的稳态过电位。使用电活性示踪剂物种的实验表明，即使在与重力相反的方向上，气泡也会增强电极表面的传质。微对流由于生长和合并气泡主导的影响，由于宏观对流的滑行气泡在硅微丝阵列阴极。在表面上保持大量小气泡的电极同时表现出低浓度的溶解氢和小的欧姆电位降，从而表现出最低的稳态过电位。结果表明，微结构电极可以在没有外部对流的情况下进行无辅助太阳能驱动的水裂解，并且无论电极相对于重力矢量的取向如何，微结构电极都可以发挥作用。
The size-distribution, coverage, electrochemical impedance, and mass-transport properties of H(2)gas-bubble films were measured for both planar and microwire-array platinized n(+)-Si cathodes performing the hydrogen-evolution reaction in 0.50 M H2SO4(aq). Inverted, planar n(+)-Si/Ti/Pt cathodes produced large, stationary bubbles which contributed to substantial increases in ohmic potential drops. In contrast, regardless of orientation, microwire array n(+)-Si/Ti/Pt cathodes exhibited a smaller layer of bubbles on the surface, and the formation of bubbles did not substantially increase the steady-state overpotential for H-2(g) production. Experiments using an electroactive tracer species indicated that even when oriented against gravity, bubbles enhanced mass transport at the electrode surface. Microconvection due to growing and coalescing bubbles dominated effects due to macroconvection of gliding bubbles on Si microwire array cathodes. Electrodes that maintained a large number of small bubbles on the surface simultaneously exhibited low concentrations of dissolved hydrogen and small ohmic potential drops, thus exhibiting the lowest steady-state overpotentials. The results indicate that microstructured electrodes can operate acceptably for unassisted solar-driven water splitting in the absence of external convection and can function regardless of the orientation of the electrode with respect to the gravitational force vector.