Electrochemical and Photoelectrochemical Detection of Hydrogen Peroxide Using Cu₂O/Cu Nanowires Decorated with TiO_2−x Deriving from MXenes

H2O2 is a major transmitter of redox signals in electrochemical processes, whose detection is relevant for various industries. Herein, we developed a new fabrication method for a Cu2O/Cu nanowire-based nonenzymatic H2O2 electrochemical sensor that was decorated with irregular TiO2–x nanoparticles deriving form Ti3C2 MXene. The TiO2–x/Cu2O/Cu-NW electrodes possess excellent selectivity, stability, and reproducibility for H2O2 detection in both EC and PEC operational modes. In the EC detection of H2O2, the TiO2–x/Cu2O/Cu-NW electrode shows a linear relationship in the range from 10 μM to 42.19 mM and a low detection limit of 0.79 μM (S/N = 3), which has a similar sensitivity but a much broader linear range compared with the commercial H2O2 analyzer (0–5.88 mM, Q45H/84, US-QContums). It also shows excellent recovery in detecting H2O2 in the real orange juice and milk samples with the recovery ranging from 96.9 to 105%, indicating the potential for practical applications. In the PEC detection of H2O2, the TiO2–x/Cu2O/Cu-NW electrode shows a lower detection limit of 59 nM (S/N = 3), which is 13 times more sensitive than the EC electrode. The enhanced PEC performance can be attributed to the formation of p–n heterojunction between TiO2–x and Cu2O, which improves light utilization and inhibits the recombination of photo-induced electrons and holes. This work illuminates the extraordinary potential of MXene-derived TiO2 in electrochemical and photoelectrochemical applications.