High-efficiency photoelectrocatalytic hydrogen generation enabled by palladium quantum dots-sensitized TiO ₂ nanotube arrays

TiO ₂ nanotube arrays (TNTAs) sensitized by palladium quantum dots (Pd QDs) exhibit highly efficient photoelectrocatalytic hydrogen generation. Vertically oriented TNTAs were prepared by a three-step electrochemical anodization. Subsequently, Pd QDs with uniform size and narrow size distribution were formed on TiO ₂ nanotubes by a modified hydrothermal reaction (i.e., yielding nanocomposites of Pd QDs deposited on TNTAs, Pd@TNTAs). By exploiting Pd@TNTA nanocomposites as both photoanode and cathode, a substantially increased photon-to-current conversion efficiency of nearly 100% at λ = 330 nm and a greatly promoted photocatalytic hydrogen production rate of 592 μmol·h ^-1·cm ^-2 under 320 mW·cm ^-2 irradiation were achieved. The synergy between nanotubular structures of TiO ₂ and uniformly dispersed Pd QDs on TiO ₂ facilitated the charge transfer of photoinduced electrons from TiO ₂ nanotubes to Pd QDs and the high activity of Pd QDs catalytic center, thereby leading to high-efficiency photoelectrocatalytic hydrogen generation.