Trotochaud Lena, Mills Thomas J, Boettcher Shannon W
Department of Chemistry and the Center for Sustainable Materials Chemistry, University of Oregon, Eugene, Oregon 97403, United States.
J Phys Chem Lett. 2013 Mar 21;4(6):931-5. doi: 10.1021/jz4002604. Epub 2013 Mar 7.
The optical properties of electrocatalysts are important for photoelectrochemical water splitting because colored catalysts on the surface of semiconductor photoelectrodes parasitically absorb photons and lower the system efficiency. We present a model that describes the coupling of colored oxygen evolution reaction (OER) electrocatalyst thin films with semiconductor photoelectrodes. We use this model to define an "optocatalytic" efficiency (Φo-c) based on experimental optical and electrokinetic data collected in basic solution. Because transition-metal oxides, hydroxides, and oxyhydroxides often exhibit electrochromism, in situ spectroelectrochemistry is used to quantify the optical absorption of active NiOx, CoOx, NiCoOx, Ni0.9Fe0.1Ox, and IrOx catalyst films at OER potentials. For the highest-activity Ni0.9Fe0.1Ox catalyst, Φo-c is maximized (0.64) for a thickness of ∼0.4 nm (∼2 monolayers). This work quantitatively shows that ultrathin catalyst films are appropriate to optimize the performance of water-splitting photoelectrodes and thus assists in the design and study of efficient photoelectrochemical water-splitting devices.
电催化剂的光学性质对于光电化学水分解至关重要，因为半导体光电极表面的有色催化剂会寄生吸收光子并降低系统效率。我们提出了一个模型，该模型描述了有色析氧反应（OER）电催化剂薄膜与半导体光电极的耦合。我们使用这个模型，根据在碱性溶液中收集的实验光学和动电数据，定义了一种“光催化”效率（Φo-c）。由于过渡金属氧化物、氢氧化物和羟基氧化物通常表现出电致变色特性，因此采用原位光谱电化学方法来量化活性NiOx、CoOx、NiCoOx、Ni0.9Fe0.1Ox和IrOx催化剂薄膜在OER电位下的光吸收。对于活性最高的Ni0.9Fe0.1Ox催化剂，当厚度约为0.4 nm（约2个单层）时，Φo-c达到最大值（0.64）。这项工作定量地表明，超薄催化剂薄膜适合于优化水分解光电极的性能，从而有助于高效光电化学水分解装置的设计和研究。
