Electrolysis of water is key technology, not only for clean energy production, but to ensure a continued supply of hydrogen beyond fossil resources, essential to the manufacture of many chemical goods other than fuels. Cobalt nanomaterials have been widely identified as a promising candidate for the anode (oxygen evolution) reaction in this process, but much work has focused on applied materials or electrode design. Given the importance of oxidation state changes Co(III) → Co(IV) in the accepted reaction mechanism, in this work we look at size effects in small (4-10 nm) cobalt nanoparticles, where the ease of oxidation for lower cobalt oxidation states is known to change with particle size. To discriminate between geometric and chemical effects we have compared the catalysts in this study to others in the literature by turnover frequency (widely used in other areas of catalysis), in addition to the more commonly employed performance metric of the overpotential required to produce a current density of 10 mA cm-2. Comparisons are drawn to key examples of using well defined nanomaterials (where the surface are of cobalt sites can be estimated). This has enabled an estimated intrinsic turnover rate of ~ 1 O2 molecule per surface Co atom per second at an overpotential of 500 mV in the oxygen evolution reaction under typical alkaline reaction conditions (pH 14.0) to be identified.

中文翻译：

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4-10 nm钴纳米颗粒对氧释放反应的催化。

水的电解不仅是清洁能源生产的关键技术，而且是确保化石资源以外的氢持续供应的关键技术，这对制造除燃料以外的许多化学产品至关重要。钴纳米材料已被广泛认为是该过程中阳极（放氧）反应的有前途的候选者，但许多工作集中在应用材料或电极设计上。考虑到在公认的反应机理中氧化态变化Co（III）→Co（IV）的重要性，在这项工作中，我们着眼于小型（4-10 nm）钴纳米颗粒的尺寸效应，其中氧化的易性可降低钴的氧化已知状态会随粒度变化。为了区分几何效应和化学效应，我们已根据周转频率（广泛用于其他催化领域），将本研究中的催化剂与文献中的其他催​​化剂进行了比较，此外还采用了产生电流所需的过电势的更常用的性能指标。密度为10 mA cm-2。比较了使用定义明确的纳米材料的关键示例（可以估计钴位点的表面）。在典型的碱性反应条件（pH 14.0）下，在氧气析出反应中，当过电位为500 mV时，估计的固有转化率约为每个表面Co原子每秒约1 O2分子。除了更常用的产生10 mA cm-2电流密度所需的过电势性能指标外。比较了使用定义明确的纳米材料的关键示例（可以估算出钴位点的表面）。在典型的碱性反应条件（pH 14.0）下，在氧气析出反应中，当过电位为500 mV时，估计的固有转化率约为每个表面Co原子每秒约1 O2分子。除了更常用的产生10 mA cm-2电流密度所需的过电势性能指标外。比较了使用定义明确的纳米材料的关键示例（可以估算出钴位点的表面）。在典型的碱性反应条件（pH 14.0）下，在氧气析出反应中，当过电位为500 mV时，估计的固有转化率约为每个表面Co原子每秒约1 O2分子。