3D Heterostructured Ti-Based Bi₂MoO₆/Pd/TiO₂ Photocatalysts for High-Efficiency Solar Light Driven Photoelectrocatalytic Hydrogen Generation

Hydrogen fuel generation using solar light via photoelectrochemical (PEC) methods can help meet growing global energy demands and decrease environmental pollution. The key to efficient PEC hydrogen production is the synthesis of solar light driven photoelectrodes with efficient charge carrier separation. Here, we designed and prepared a ternary Bi2MoO6/Pd/TiO2 photoelectrode composed of Bi2MoO6 nanosheets, Pd nanoparticles (NPs), and TiO2 nanotube arrays (NTAs) on a Ti substrate using electrochemical methods. This novel photoelectrode had good visible light absorbance and significantly improved PEC hydrogen production rates (∼5- and >15-times higher under UV–vis and visible light irradiation, respectively, compared with TiO2NTAs). The interfacial charge transfer mechanism of Bi2MoO6/Pd/TiO2 NTAs was comprehensively studied by comparing its PEC and photoelectrocatalytic performance with that of other TiO2 NTAs (i.e., Pd/TiO2 NTAs, Bi2MoO6/TiO2 NTAs, and Pd/Bi2MoO6/TiO2 NTAs). For Bi2MoO6/Pd/TiO2 NTAs, Pd NPs homogeneously dispersed across the inside and outside of TiO2 nanotube walls helped to tightly anchor Bi2MoO6 nanosheets onto the TiO2 surface, forming a ternary 3D heterostructure. This structure facilitated interfacial electron injection from Bi2MoO6 to TiO2, accelerating the separation of the photogenerated electron–hole pairs. Significantly enhanced photocurrent response and hydrogen production rate were achieved compared with other TiO2 NTAs. This 3D ternary semiconductor/metal/semiconductor heterojunction provides a viable approach for designing and synthesizing highly efficient novel photocatalysts that can effectively utilize solar energy.