Electrochemical and Photoelectrochemical Detection of Hydrogen Peroxide Using Cu 2 O/Cu Nanowires Decorated with TiO 2- x Deriving from MXenes.

H 2 O 2 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 Cu 2 O/Cu nanowire-based nonenzymatic H 2 O 2 electrochemical sensor that was decorated with irregular TiO 2- x nanoparticles deriving form Ti 3 C 2 MXene. The TiO 2- x /Cu 2 O/Cu-NW electrodes possess excellent selectivity, stability, and reproducibility for H 2 O 2 detection in both EC and PEC operational modes. In the EC detection of H 2 O 2 , the TiO 2- x /Cu 2 O/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 H 2 O 2 analyzer (0-5.88 mM, Q45H/84, US-QContums). It also shows excellent recovery in detecting H 2 O 2 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 H 2 O 2 , the TiO 2- x /Cu 2 O/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 TiO 2- x and Cu 2 O, which improves light utilization and inhibits the recombination of photo-induced electrons and holes. This work illuminates the extraordinary potential of MXene-derived TiO 2 in electrochemical and photoelectrochemical applications.