Self-Assembled α-Fe₂O₃@Co₃O₄/Graphene Quantum Dot Core–Hybrid Shell Wormlike Nanoarrays with Synergistic Effects for Photoelectrochemical Water Oxidation

Hematite (α-Fe2O3) core–cocatalyst shell nanoarchitectures with ultrathin hybrid shells are promising to maximize photoelectrochemical (PEC) water oxidation performance of Fe2O3-based photoelectrodes, but their fabrication presents formidable challenges. For the first time, a wormlike nanostructured α-Fe2O3@Co3O4/graphene quantum dot (GQD) core–hybrid shell nanoarray is synthesized via self-assembly, showing an onset potential of 0.63 V (vs the reversible hydrogen electrode (RHE)) and a photocurrent density of 3.63 mA cm–2 at 1.23 V (vs RHE). This performance is superior to those of reported Fe2O3-based heterojunction photoanodes and among the best reported for Fe2O3-based photoanodes. The outstanding performance is due to the Co3O4/GQD shell significantly promoting charge separation and transfer and hole injection as well as great synergistic effects between GQDs and Co3O4. This work not only fabricates a low-cost photoanode with record-high water oxidation performance and offers scientific insights into the enhancement mechanism but also provides a facile, economical, and universal strategy to self-assemble conformal, ultrathin hybrid shells on three-dimensional (3-D) complex nanostructures, which have broad applications in the fields of energy, environment, and sensing.