Tamirat Andebet Gedamu, Dubale Amare Aregahegn, Su Wei-Nien, Chen Hung-Ming, Hwang Bing-Joe
NanoElectrochemistry Laboratory, Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan.
Phys Chem Chem Phys. 2017 Aug 9;19(31):20881-20890. doi: 10.1039/c7cp02890c.
Hematite (α-FeO) is a suitable candidate for photoelectrochemical water splitting due to its well-suited band structure, stability, and availability. However, water splitting using a low external potential is the major challenge that limits the practical application of hematite. Here, we achieve a very low onset potential using a sequential surface treatment approach to overcome two fundamental limiting factors, sluggish hole transfer, and interfacial recombination, independently. First, a heavily doped FeSnO surface passivation layer was created by Sn surface treatment which can robustly inhibit interfacial recombination. Then, an NiOOH catalyst layer was deposited that greatly enhances the charge transfer process across the passivated electrode/electrolyte interface. By exploiting this approach, the optimized sequentially treated photoanode (FeO/FeSnO/NiOOH) exhibits a low photocurrent onset potential of 0.49 V vs. RHE and a saturated photocurrent density of 2.4 mA cm V at 1.5 V vs. RHE. Transient photocurrent and impedance spectroscopy measurements further reveal that the combined FeSnO/NiOOH layers reduce interfacial recombination and enhance charge transfer across the electrode/electrolyte interface. The results provide convincing evidence that it is possible to address the problems of surface trap recombination and sluggish catalysis independently by employing surface passivation layers first and catalysts later sequentially.
赤铁矿（α-Fe₂O₃）因其合适的能带结构、稳定性和可得性，是光电化学水分解的合适候选材料。然而，使用低外部电势进行水分解是限制赤铁矿实际应用的主要挑战。在此，我们采用顺序表面处理方法实现了非常低的起始电势，以分别克服两个基本限制因素，即缓慢的空穴转移和界面复合。首先，通过Sn表面处理形成了重掺杂的FeSnO表面钝化层，它可以有效抑制界面复合。然后，沉积了NiOOH催化剂层，这大大增强了电荷在钝化电极/电解质界面的转移过程。通过采用这种方法，优化后的顺序处理光阳极（Fe₂O₃/FeSnO/NiOOH）相对于可逆氢电极（RHE）表现出0.49 V的低光电流起始电势，在1.5 V相对于RHE时的饱和光电流密度为2.4 mA cm⁻²。瞬态光电流和阻抗谱测量进一步表明，FeSnO/NiOOH复合层减少了界面复合，并增强了电荷在电极/电解质界面的转移。结果提供了令人信服的证据，即通过先采用表面钝化层，然后依次使用催化剂，可以分别解决表面陷阱复合和缓慢催化的问题。
