Piezo-photoelectric all-in-one coaxial hierarchical TiO2-BaTiO3-CuInS2 heterostructure for synergistic water splitting

Rational multiple-field coupling, component control, and microarchitectures design for utilization of multiform driving forces as well as benefiting charge-carrier separation and migration is considered to be an outstanding approach to improve water splitting efficiency for alleviating increasing environmental problems. Herein, a novel piezo-photoelectric catalyst, coaxial TiO2-BaTiO3-CuInS2 heterostructures, was designed for efficient hydrogen production, synergistically driven by mechanical force, electricity, and light. The vertical growth of TiO2 nanorods guarantees sufficient generation of photoinduced charges and their fast migration. Electric field generated by the piezoelectric BaTiO3 shell under a mechanical driving force will promote the separation and transfer of photogenerated charge carriers, thereby minimizing the probability of charge recombination. The further incorporation of the outermost layer of CuInS2 is beneficial to broaden light harvesting. Of particular importance is the cascade band arrangement of the three different functional components, which greatly enhances the transfer of photo- and piezoelectrically induced charges. With the synergy of enhanced light harvesting, energy band engineering, and nanostructure interfacial design, the fabricated TiO2-BaTiO3-CuInS2 photoelectrode has achieved significant enhancement of piezo-photoelectric hydrogen evolution efficiency and could be expanded for pollutant decomposition. This simple yet general strategy provides valuable guidance for cooperatively capitalizing on piezoelectricity to engineer high-performing energy conversion and environmental protection.