Abstract Synergistic effects as a result of combining different photoactive materials provide a promising pathway to improve the photoelectrochemical performance in heterojunction devices for solar water splitting. The photoelectrochemical characteristics of tungsten trioxide (WO3) and bismuth vanadate (BiVO4) have been studied, comparing the single-phase materials with two heterojunction systems based on a WO3 underlayer and a thin, spin-coated BiVO4 top layer, using two types of underlayer: (i) a nanorod-based WO3 substrate prepared by hydrothermal methods (nr-WO3/BiVO4); and (ii) a spin-coated thin, compact WO3 substrate (pl-WO3/BiVO4). Intensity-modulated photocurrent spectroscopy (IMPS) was used to determine the charge separation efficiency, internal and external quantum efficiencies, and process time constants for the four systems in a phosphate buffer at pH 7, both without and with an added hole scavenger, Na2SO3. The heterojunction systems show excellent performance, which is ascribed to the superior capability of WO3 to extract photogenerated electrons from the BiVO4 film that acts as the main absorber. IMPS convincingly shows that the heterojunction configuration prevents surface recombination at the BiVO4 /electrolyte interface, as well as the detrimental surface modification generally observed for WO3 photoelectrodes. The improved electron transport properties of the nr-WO3 substrate and the large area of the heterojunction interface result in better performance for nr-WO3/BiVO4, where at 455 nm water photo-oxidation is quantitative. For the single-phase BiVO4 photoelectrodes, an interesting photocurrent switching phenomenon is observed in the presence of the hole scavenger, indicating the intricate interplay between electron trapping and hole charge transfer; this phenomenon is prevented by the heterojunction structure because of the rapid electron extraction by WO3. These results show that IMPS gives detailed information on the reasons for the excellent performance of heterojunction systems, providing opportunities to design new, more efficient solar water splitting systems.

中文翻译：

---

WO3/BiVO4异质结系统电荷载流子动力学的强度调制光电流光谱研究

摘要 结合不同光敏材料产生的协同效应为提高太阳能水分解异质结器件的光电化学性能提供了一条有前景的途径。研究了三氧化钨 (WO3) 和钒酸铋 (BiVO4) 的光电化学特性，比较了单相材料与基于 WO3 底层和薄旋涂 BiVO4 顶层的两种异质结系统，使用两种类型的底层: (i) 通过水热法制备的基于纳米棒的 WO3 基材 (nr-WO3/BiVO4)；(ii) 旋涂的薄而紧凑的 WO3 衬底 (pl-WO3/BiVO4)。强度调制光电流光谱 (IMPS) 用于确定电荷分离效率、内部和外部量子效率、四个系统在 pH 7 的磷酸盐缓冲液中的处理时间常数，无论是否添加空穴清除剂 Na2SO3。异质结系统表现出优异的性能，这归因于 WO3 从作为主要吸收体的 BiVO4 薄膜中提取光生电子的卓越能力。IMPS 令人信服地表明，异质结构型可防止 BiVO4/电解质界面处的表面复合，以及通常对 WO3 光电极观察到的有害表面改性。nr-WO3 衬底的改进电子传输特性和异质结界面的大面积导致 nr-WO3/BiVO4 的性能更好，其中在 455 nm 处水光氧化是定量的。对于单相 BiVO4 光电极，在空穴清除剂的存在下观察到一个有趣的光电流转换现象，表明电子俘获和空穴电荷转移之间复杂的相互作用；由于 WO3 的快速电子提取，异质结结构可以防止这种现象。这些结果表明，IMPS 提供了有关异质结系统优异性能原因的详细信息，为设计新的、更高效的太阳能水分解系统提供了机会。