Layer-by-layer assembly: an emerging, tailored and robust platform for solar water splitting

Photoelectrochemical (PEC) water splitting represents a highly promising technology to convert solar energy into clean and renewable chemical fuels. Among the various strategies utilized for customizing photoelectrodes, layer-by-layer (LbL) assembly has emerged as a green, simple, and easily accessible technique for rationally constructing multilayered heterostructures in terms of versatility, flexibility, and atomic-level interface configuration modulation. However, precise design of robust photoelectrodes based on LbL assembly still remains in the exploratory stage. This review comprehensively summarizes the recent advancements in the fabrication of composite multilayer photoanodes via LbL assembly, highlighting the LbL assembly construction with diverse substrates (e.g., metal oxides, transition metal sulfides) and building blocks of varying sizes and dimensions (e.g., quantum dots, nanoclusters, nanoparticles, nanosheets). Furthermore, this review underscores the role of these building blocks in extending the light absorption and improving the solar water oxidation performance. Most importantly, the latest endeavors devoted to mediating directional charge transfer routes in artificial PEC systems are specifically summarized. Finally, prospects and challenges of LbL assembly technology in photoelectrode engineering for PEC water splitting are outlined, aiming to inspire innovative strategies for the smart design of composite nanostructured photoelectrodes towards solar energy conversion.