The green transition, despite recent advances in cobalt-free battery technologies, is still highly dependent on the availability of critical cobalt-based materials. Consequently, there has been increasing interest towards the development of new methods that maximize critical metals recovery from industrial hydrometallurgical solutions. In the current study, direct anodic oxidation of cobalt species from cobalt chloride solutions was studied as one alternative future strategy for cobalt recovery. Electrochemical methods were used (cyclic voltammetry, potentiostatic anodic deposition) and the effect of pH, temperature, and the concentration of cobalt and chloride ions on cobalt precipitation were investigated. The increase of pH and temperature was shown to stabilize the electrochemical oxidation of cobalt, while a decrease in cobalt concentration had a negative effect on precipitation. Scanning Electron Microscope, Atomic Force Microscopy and X-ray Photoelectron Spectroscopy were exploited to evaluate the morphology, structure, and composition of obtained anodic product. Calculated for potentiostatic anodic deposition (at highest studied potential of 1300 mV vs. Ag/AgCl) nucleation mechanism shows that the rate of nucleation for oxygen-cobalt species is faster than the subsequent growth rate of nuclei (instantaneous mechanism). XPS results confirmed that mixed CoO/Co(OH)/CoOOH precipitate could be obtained by optimized anodic potentiostatic deposition in the range from 900 to 1150 mV and pH from 3 to 6 at 60 °C.

中文翻译：

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氯化物介质中钴的电化学氧化

尽管无钴电池技术最近取得了进展，但绿色转型仍然高度依赖于关键钴基材料的可用性。因此，人们对开发新方法越来越感兴趣，以最大限度地从工业湿法冶金解决方案中回收关键金属。在当前的研究中，研究了从氯化钴溶液中直接阳极氧化钴物质，作为钴回收的一种替代未来策略。使用电化学方法（循环伏安法、恒电位阳极沉积），研究了 pH、温度以及钴和氯离子浓度对钴沉淀的影响。 pH 值和温度的升高可以稳定钴的电化学氧化，而钴浓度的降低则对沉淀产生负面影响。利用扫描电子显微镜、原子力显微镜和X射线光电子能谱评估所得阳极产物的形貌、结构和成分。计算恒电位阳极沉积（相对于 Ag/AgCl 的最高研究电位 1300 mV）成核机制表明，氧-钴物质的成核速率比随后的核生长速率更快（瞬时机制）。 XPS 结果证实，在 60 °C 下，通过在 900 至 1150 mV 范围内、pH 值从 3 至 6 范围内优化阳极恒电位沉积，可以获得混合的 CoO/Co(OH)/CoOOH 沉淀。