Novel highly active and self-healing Co(CO3)xOHy cocatalysts on BiVO4 photoanodes for effective solar water oxidation,Journal of Materials Chemistry A

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Novel highly active and self-healing Co(CO3)xOHy cocatalysts on BiVO4 photoanodes for effective solar water oxidation
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020/01/06 , DOI: 10.1039/c9ta13122a
Lijun Wu _{1,

2,

3,

4,

5} , Lei Wang _{1,

2,

3,

4,

5} , Jie Zhu _{1,

2,

3,

4,

5} , Mao Sun _{1,

2,

3,

4,

5} , Xianhu Liu _{5,

6,

7,

8,

9} , Patrik Schmuki _{10,

11,

12,

13,

14} , Jun Zhang _{1,

2,

3,

4,

5}

Affiliation

Recent reports show that Co-Pi cocatalysts on some photoanodes, such as Fe₂O₃ or BiVO₄, accelerate the surface water oxidation rate, acting as a hole extracting layer that improves charge separation or as a “surface passivation agent”. In contrast, on semiconductors such as BiVO₄, deposition of classic Co-based oxygen evolution catalysts (e.g. Co₃O₄, CoOOH) leads to a relatively low improvement of the photoelectrochemical (PEC) performance. This illustrates that even though a species may be an excellent electrocatalyst, it may not be an effective co-catalyst for PEC reactions. Clearly, for different semiconductors there is a need to directly identify and prepare specific, highly active and low-cost cocatalysts for promoting PEC water oxidation. Co(CO₃)_0.5(OH)·0.11H₂O (or in general Co(CO₃)_xOH_y) is usually used as a precursor to synthesize a range of Co-based efficient electrocatalysts. Herein, we for the first time show that Co(CO₃)_xOH_y on BiVO₄ provides an excellent oxygen evolution reaction activity, even close to the so far most efficient dual-layer FeOOH/NiOOH cocatalysts. Decoration of BiVO₄ with Co(CO₃)_xOH_y and the resulting photoanode shows a remarkable enhancement of photocurrent, achieving a photocurrent density of 5.0 mA cm⁻² at 1.23 V_RHE with an onset potential of 0.3 V_RHE, which is one of the highest PEC activities of BiVO₄ reported up to now. The outstanding PEC performance can be attributed to the improvement of charge separation and transfer efficiency caused by a uniform thin coating of Co(CO₃)_xOH_y. The Co(CO₃)_xOH_y exhibits the highest density of active sites, the highest surface area, and the best OER activity among the investigated cobalt-based cocatalysts. Remarkably, the Co(CO₃)_xOH_y also displays a self-healing function in borate buffered electrolytes. Therefore, this work not only describes low-cost but highly active cobalt-based catalysts for PEC solar water oxidation, but additionally shows a self-repair function of this system.

中文翻译：

在BiVO4光阳极上的新型高活性和自修复Co（CO3）xOHy助催化剂可有效地氧化太阳能

最近的报告表明，某些光阳极（例如Fe ₂ O ₃或BiVO _4）上的Co-Pi助催化剂可加速表面水的氧化速率，充当改善电荷分离的空穴提取层或充当“表面钝化剂”。相反，在BiVO ₄等半导体上，经典的Co基氧析出催化剂（例如Co ₃ O ₄，例如，CoOOH）导致光电化学（PEC）性能的改善相对较低。这说明即使一种物质可能是极好的电催化剂，也可能不是PEC反应的有效助催化剂。显然，对于不同的半导体，需要直接鉴定和制备特定的，高活性和低成本的助催化剂来促进PEC水的氧化。Co（CO ₃）_0.5（OH）·0.11H ₂ O（或者通常是Co（CO ₃）_x OH _y）通常用作合成一系列Co基高效电催化剂的前体。在这里，我们第一次显示了BiVO上的Co（CO ₃）_x OH _y_图4提供了优异的氧释放反应活性，甚至接近迄今为止最有效的双层FeOOH / NiOOH助催化剂。用Co（CO₃）_x OH_y装饰BiVO₄以及所得的光电阳极显示出显着的光电流增强，在1.23 V_RHE时实现了5.0 mA cm^-2的光电流密度，起始电位为0.3 V_RHE，即到目前为止，BiVO₄的最高PEC活性报告。出色的PEC性能可归因于Co（CO₃）_x均匀薄涂层导致的电荷分离和转移效率的提高OH _ÿ。在所研究的钴基助催化剂中，Co（CO ₃）_x OH _y表现出最高的活性中心密度，最高的表面积和最佳的OER活性。值得注意的是，Co（CO ₃）_x OH _y在硼酸盐缓冲电解质中也显示出自愈功能。因此，这项工作不仅描述了用于PEC太阳能氧化的低成本，高活性钴基催化剂，而且还显示了该系统的自修复功能。

更新日期：2020-02-10

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