Tuning Intermediate Bands of Protective Coatings to Reach the Bulk-Recombination Limit of Stable Water-Oxidation GaP Photoanodes,Advanced Energy Materials

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Tuning Intermediate Bands of Protective Coatings to Reach the Bulk-Recombination Limit of Stable Water-Oxidation GaP Photoanodes
Advanced Energy Materials ( IF 24.4 ) Pub Date : 2022-06-17 , DOI: 10.1002/aenm.202201314
Xin Shen _{1,

2} , Tianshuo Zhao _{1,

2} , Haoqing Su _{1,

2} , Meiqi Yang _{1,

2} , Jiaye Chen _{1,

2} , Yulin Liu _{1,

2} , Rito Yanagi _{1,

2} , Devan Solanki _{1,

2} , Shu Hu _{1,

2}

Affiliation

Stable photoelectrochemical solar fuel production requires protective coatings to achieve effective charge separation, transport, and injection at the semiconductor–liquid interfaces, implying that the coating should energetically align its intermediate band (IB) with both the photoabsorber's band edge and co-catalyst's potentials. Yet approaches to adjust coating IB positions to accommodate various semiconductor light absorbers for constructing efficient and stable photoelectrodes have not been developed. Herein, three types of transition metal (M = Mn²⁺, Mn³⁺, and Cr³⁺ ions) alloyed TiO₂ coatings are discovered using atomic layer deposition (ALD). The IB energetics of these coatings are characterized by X-ray photoelectron spectroscopy and are found to be tunable inside the TiO₂ bandgap, through varying ALD growth conditions. By applying these coatings to n-type GaP and integrating with IrO_x co-catalysts, the water-oxidation J–E performance is comparable to an uncoated corroding GaP photoanode. It reaches the bulk recombination limit of the GaP and achieves ≈28% absorbed photon to current efficiency under 475-nm light excitation (6.48 mW cm⁻²) and 100-h stable water oxidation. The outstanding performance and stability are attributed to the efficient charge separation and hole transport, as allowed by the energy alignment of the coating IB and the GaP valence band edge.

中文翻译：

调整保护涂层的中间带以达到稳定的水氧化 GaP 光电阳极的体重组极限

稳定的光电化学太阳能燃料生产需要保护涂层以在半导体-液体界面实现有效的电荷分离、传输和注入，这意味着涂层应在能量上使其中间带 (IB) 与光吸收剂的带边和助催化剂的电位对齐。然而，尚未开发出调整涂层 IB 位置以适应各种半导体光吸收剂以构建高效且稳定的光电极的方法。在此，三种过渡金属（M=Mn ²⁺、Mn ³⁺和Cr ³⁺离子）合金化TiO ₂涂层是使用原子层沉积 (ALD) 发现的。这些涂层的 IB 能量通过 X 射线光电子能谱来表征，并且发现在 TiO ₂带隙内可通过不同的 ALD 生长条件进行调节。通过将这些涂层应用于 n 型 GaP 并与 IrO _x助催化剂结合，水氧化J - E性能可与未涂层的腐蚀 GaP 光阳极相媲美。它达到了 GaP 的体复合极限，并在 475 nm 光激发（6.48 mW cm ^-2) 和 100 小时稳定的水氧化。出色的性能和稳定性归因于有效的电荷分离和空穴传输，这是涂层 IB 和 GaP 价带边缘的能量对齐所允许的。

更新日期：2022-06-17

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