Carbon Quantum Dot-Mediated\nCoAl-Layered Double Hydroxide\non Hematite for Boosted Photoelectrochemical Sensing of Hydrogen Peroxide

As an important compound in various industries and metabolic\nprocesses\nin the human body, high concentrations of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) can cause serious injuries to humans and other\norganisms. Thus, it is of great significance to develop a rapid, sensitive,\nand practical method for the detection of H<sub>2</sub>O<sub>2</sub>. Herein, carbon quantum dot-mediated CoAl-layered double hydroxide\n(CQDs/CoAl-LDH) was decorated on a hematite (α-Fe<sub>2</sub>O<sub>3</sub>) photoelectrode via a simple one-pot hydrothermal method.\nThe resultant CQDs/CoAl-LDH/α-Fe<sub>2</sub>O<sub>3</sub> exhibited\nexcellent photoelectrochemical (PEC) sensing toward H<sub>2</sub>O<sub>2</sub> with high sensitivities of 92.10 and 39.27 μA mM<sup>–1</sup> cm<sup>–2</sup> in the linear range of 0.001–0.9\nand 0.9–2 mM, respectively, and low limit of detection (0.02\nμM, S/N = 3) at 0 V vs SCE, as well as good selectivity, stability,\nreproducibility, and reliability. The investigation of the mechanism\nrevealed that CQDs could not only mediate the growth of CoAl-LDH to\nexpose active sites but also improve the electroconductivity of CoAl-LDH\nto facilitate charge transfer, while CoAl-LDH could rapidly extract\nphotogenerated holes to improve charge separation and provide catalytic\nactive sites for H<sub>2</sub>O<sub>2</sub> oxidation. The synergistic\neffect of the CQDs and CoAl-LDH significantly boosted the PEC activity\nof α-Fe<sub>2</sub>O<sub>3</sub> for H<sub>2</sub>O<sub>2</sub> oxidation. The strategy for boosting the PEC performance is of great\nimportance for other semiconductor photoelectrodes.