Carbon Quantum Dot-Mediated CoAl-Layered Double Hydroxide on Hematite for Boosted Photoelectrochemical Sensing of Hydrogen Peroxide

As an important compound in various industries and metabolic processes in the human body, high concentrations of hydrogen peroxide (H2O2) can cause serious injuries to humans and other organisms. Thus, it is of great significance to develop a rapid, sensitive, and practical method for the detection of H2O2. Herein, carbon quantum dot-mediated CoAl-layered double hydroxide (CQDs/CoAl-LDH) was decorated on a hematite (α-Fe2O3) photoelectrode via a simple one-pot hydrothermal method. The resultant CQDs/CoAl-LDH/α-Fe2O3 exhibited excellent photoelectrochemical (PEC) sensing toward H2O2 with high sensitivities of 92.10 and 39.27 μA mM–1 cm–2 in the linear range of 0.001–0.9 and 0.9–2 mM, respectively, and low limit of detection (0.02 μM, S/N = 3) at 0 V vs SCE, as well as good selectivity, stability, reproducibility, and reliability. The investigation of the mechanism revealed that CQDs could not only mediate the growth of CoAl-LDH to expose active sites but also improve the electroconductivity of CoAl-LDH to facilitate charge transfer, while CoAl-LDH could rapidly extract photogenerated holes to improve charge separation and provide catalytic active sites for H2O2 oxidation. The synergistic effect of the CQDs and CoAl-LDH significantly boosted the PEC activity of α-Fe2O3 for H2O2 oxidation. The strategy for boosting the PEC performance is of great importance for other semiconductor photoelectrodes.