Graphene Oxide Covered WO₃ Nanosheet Arrays as Photoelectrode for Photoelectrochemical Detection of Trace H₂O₂

Accurate detection of trace hydrogen peroxide (H 2 O 2 ) by the anode photoelectrochemical (PEC) method is highly attractive in the modern chemical industry. However, the sluggish hole migration kinetics in photocatalysts are severely unfavorable for hole enrichment on the photoanodic surface, limiting the method’s sensitivity and detection limit in practical applications. Herein, we proposed graphene oxide (GO) with high conductivity as cocatalyst to capture and aggregate hole tactics for tackling this formidable mission. As a proof of concept, GO covered tungsten trioxide (WO 3 ) nanosheet arrays as photoelectrode were selected and cast as a prototype. The as-synthesized WO 3 nanosheet only showed a thickness of 120–140 nm. Optical and structural characterizations demonstrate that GO was validated to accelerate the oxidation of H 2 O 2 to O 2 rather than • OH by improving the hole density on the surface of GO/WO 3 and reducing the overpotential of H 2 O 2 decomposition. Subsequently, it helps to boost the oxidation current of H 2 O 2 on the GO/WO 3 photoanode (24.7 μA cm −2 in 2 mM H 2 O 2 ) at a lower potential of 0.7 V vs RHE. As a result, the lower minimum detection limit and sensitivity of H 2 O 2 detection by the GO/WO 3 photoanode are up to 0.1 mM and 8.14 μA cm −2 mM −1, respectively, which are 0.25 (0.4 mM) and 2.91 (2.79 μA cm −2 mM −1 ) times sensitive than that of WO 3 photoanode. This work affords a strategy to boost the sensitivity and detection limit of trace H 2 O 2 detection, which may have applications in biological analysis and the early detection of diseases.