Abstract We examined the kinetic and transport processes involved in the production of H 2 from water with Co 2+ as the electroactive species being oxidized at a Ni electrode in 40 wt% KOH at 318 K. The relevant transport parameters such as electrochemical rate constants, transfer coefficients, diffusion coefficients, and adsorption coefficients were estimated from a combination of cyclic voltammetry experiments and numerical modeling. Fourteen parameters characterize the electrochemical reaction on a clean electrode, with the Butler-Volmer equation describing the electron transfer step to solution and to adsorption bound electroactive species. A Frumkin Isotherm describes the thermodynamics of the adsorption process. Experimentally realized anodic current densities at cell voltages below 1.23 V were circa 1 mA cm −2 , a hydrogen production level far too low for commercial viability of the solar thermal decoupled water electrolysis process. However, our 3-D finite element model of the electrochemical cell operating at 318 K, suggests that current densities approaching 20 mA cm −2 can be reached in a cell with forced convection and a solvent that increases the solubility of CoO by a factor of 10 above that for KOH. Finally, the current density calculations from the perspective of industrial viability suggest producing porous metal anodes for which the actual surface area is 10–100 times larger than the electrode’s planar area.

中文翻译：

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太阳能热解耦水电解过程二：阳极电化学反应的扩展研究

摘要 我们研究了从水中以 Co 2+ 作为电活性物质在 40 wt% KOH 中在 318 K 下氧化的电活性物质 H 2 所涉及的动力学和传输过程。相关的传输参数如电化学速率常数、转移系数、扩散系数和吸附系数是通过循环伏安实验和数值模拟的组合来估计的。十四个参数表征清洁电极上的电化学反应，Butler-Volmer 方程描述了电子转移到溶液和吸附结合电活性物质的步骤。Frumkin 等温线描述了吸附过程的热力学。在电池电压低于 1.23 V 时实验实现的阳极电流密度约为 1 mA cm -2 ，对于太阳能热解耦水电解工艺的商业可行性而言，氢气生产水平太低。然而，我们在 318 K 下运行的电化学电池的 3-D 有限元模型表明，在具有强制对流和溶剂的电池中可以达到接近 20 mA cm -2 的电流密度，该溶剂将 CoO 的溶解度增加了一个因子比 KOH 高 10。最后，从工业可行性角度计算的电流密度表明，生产实际表面积比电极平面面积大 10-100 倍的多孔金属阳极。表明在具有强制对流和溶剂的电池中可以达到接近 20 mA cm -2 的电流密度，该溶剂将 CoO 的溶解度提高 10 倍于 KOH 的溶解度。最后，从工业可行性角度计算的电流密度表明，生产实际表面积比电极平面面积大 10-100 倍的多孔金属阳极。表明在具有强制对流和溶剂的电池中可以达到接近 20 mA cm -2 的电流密度，该溶剂将 CoO 的溶解度提高 10 倍于 KOH 的溶解度。最后，从工业可行性角度计算的电流密度表明，生产实际表面积比电极平面面积大 10-100 倍的多孔金属阳极。