School of Pharmaceutical and Chemical Engineering, Taizhou University, Jiaojiang 318000, China.
Research Center for Sustainable Technologies, Faculty of Engineering, Computing and Science, Swinburne University of Technology, Jalan Simpang Tiga, 93350 Kuching, Sarawak, Malaysia.
J Colloid Interface Sci. 2023 Aug 15;644:533-545. doi: 10.1016/j.jcis.2023.03.180. Epub 2023 Mar 31.
Metal-organic polymers (MOPs) can enhance the photoelectrochemical (PEC) water oxidation performance of BiVO photoanodes, but their PEC mechanisms have yet to be comprehended. In this work, we constructed an active and stable composite photoelectrode by overlaying a uniform MOP on the BiVO surface using Fe as the metal ions and 2,5-dihydroxyterephthalic acid (DHTA) as ligand. Such modification on the BiVO surface yielded a core-shell structure that could effectively enhance the PEC water oxidation activity of the BiVO photoanode. Our intensity-modulated photocurrent spectroscopy analysis revealed that the MOP overlayer could concurrently reduce the surface charge recombination rate constant (k) and enhance the charge transfer rate constant (k), thus accelerating water oxidation activity. These phenomena can be ascribed to the passivation of the surface that inhibits the recombination of the charge carrier and the MOP catalytic layer that improves the hole transfer. Our rate law analysis also demonstrated that the MOP coverage shifted the reaction order of the BiVO photoanode from the third-order to the first-order, resulting in a more favorable rate-determining step where only one hole accumulation is required to overcome water oxidation. This work provides new insights into the reaction mechanism of MOP-modified semiconductor photoanodes.
金属-有机聚合物（MOPs）可以提高 BiVO 光阳极的光电化学（PEC）水氧化性能，但它们的 PEC 机制尚未被理解。在这项工作中，我们通过使用 Fe 作为金属离子和 2,5-二羟基对苯二甲酸（DHTA）作为配体，在 BiVO 表面覆盖一层均匀的 MOP，构建了一种活性和稳定的复合光电极。这种在 BiVO 表面的修饰产生了一种核壳结构，可以有效地提高 BiVO 光阳极的 PEC 水氧化活性。我们的强度调制光电流光谱分析表明，MOP 覆盖层可以同时降低表面电荷复合速率常数（k）并提高电荷转移速率常数（k），从而加速水氧化活性。这些现象可以归因于表面的钝化抑制了载流子的复合，以及 MOP 催化层促进了空穴的转移。我们的速率定律分析还表明，MOP 覆盖率将 BiVO 光阳极的反应级数从三级转变为一级，从而形成一个更有利的速率决定步骤，只需要一个空穴积累就可以克服水氧化。这项工作为 MOP 修饰半导体光阳极的反应机制提供了新的见解。
