Bera Susanta, Lee Sol A, Lee Woo-Jae, Kim Ji-Hee, Kim Changyeon, Kim Hyun Gu, Khan Hasmat, Jana Sunirmal, Jang Ho Won, Kwon Se-Hun
School of Materials Science and Engineering, Pusan National University, Busan 46241, Republic of Korea.
Global Frontier R&D Center for Hybrid Interface Materials, Pusan National University, Busan 46241, Republic of Korea.
ACS Appl Mater Interfaces. 2021 Mar 31;13(12):14291-14301. doi: 10.1021/acsami.1c00958. Epub 2021 Mar 18.
To fabricate high efficiency photoanodes for water oxidation, it is highly required to engineer their nanoporous architecture and interface to improve the charge separation and transport efficiency. By focusing on this aspect, we developed hierarchical nanoporous BiVO (BV) from solution processed two-dimensional BiOI (BI) crystals. The orientation of the BI crystals was controlled by changing the solvent volume ratios of ethylene glycol (EG) to ethanol (ET), which resulted in different hierarchical and planar BV morphologies through a chemical treatment followed by thermal heating. The morphology with optimal particle dimension, connectivity, and porosity can offer a highly enhanced electrochemically active surface area (ECSA). The hierarchical BV owning a maximum ECSA showed the best photoelectrochemical (PEC) performance in terms of the highest photocurrent density and charge separation efficiency. However, to further improve the performance of the electrode, conformal and ultrathin SnO underlayers were deposited by a powerful atomic layer deposition technique at the interface to effectively block the defect density, which significantly improved the photocurrents as high as 3.25 mA/cm for sulfite oxidation and 2.55 mA/cm for water oxidation at 0.6 V versus the reversible hydrogen electrode (RHE). The electrode possessed record charge separation efficiency of 97.1% and charge transfer efficiency of 90.1% at 1.23 V among to-date reported BiVO-based photoanodes for water oxidation. Furthermore, a maximum applied bias photon-to-current efficiency (ABPE) of 1.61% was found at a potential as low as 0.6 V, which is highly promising to make a tandem cell. These results indicate that the construction of the hierarchical nanoporous photoanode with an enhanced ECSA and its proper interface engineering can significantly improve the PEC performance.
为了制备用于水氧化的高效光阳极，迫切需要对其纳米多孔结构和界面进行设计，以提高电荷分离和传输效率。基于这一点，我们通过溶液处理二维BiOI（BI）晶体开发了分级纳米多孔BiVO（BV）。通过改变乙二醇（EG）与乙醇（ET）的溶剂体积比来控制BI晶体的取向，经过化学处理和热加热后，这导致了不同的分级和平面BV形态。具有最佳颗粒尺寸、连通性和孔隙率的形态可以提供高度增强的电化学活性表面积（ECSA）。拥有最大ECSA的分级BV在光电流密度和电荷分离效率方面表现出最佳的光电化学（PEC）性能。然而，为了进一步提高电极性能，通过强大的原子层沉积技术在界面处沉积了保形且超薄的SnO底层，以有效阻挡缺陷密度，这显著提高了光电流，在相对于可逆氢电极（RHE）为0.6 V时，亚硫酸盐氧化的光电流高达3.25 mA/cm²，水氧化的光电流为2.55 mA/cm²。在迄今为止报道的用于水氧化的基于BiVO的光阳极中，该电极在1.23 V时具有创纪录的97.1%的电荷分离效率和90.1%的电荷转移效率。此外，在低至0.6 V的电位下发现最大应用偏压光子到电流效率（ABPE）为1.61%，这对于制造串联电池非常有前景。这些结果表明，构建具有增强ECSA的分级纳米多孔光阳极及其适当的界面工程可以显著提高PEC性能。
