A Photoelectrochemical Sensor Based on TiO2 Nanotube Arrays Decorated with Nickel-Cobalt Layered Double Hydroxides for the Effective and Sensitive Detection of Chromium(VI)

Developing stable and highly efficient photoactive materials is desirable to their extensive application in photoelectrochemical (PEC) sensors. Herein, a nickel–cobalt layered double hydroxides (NiCo-LDHs) cocatalyst-modified TiO2 nanotube arrays (TiO2NTAs) photoelectrode (NiCo-LDHs/TiO2NTAs/Ti) was fabricated and used to construct a PEC sensing platform for hexavalent chromium, Cr(VI), detection. The resultant NiCo-LDHs/TiO2NTAs/Ti showed higher photocatalytic water-splitting activity than the pristine TiO2NTAs/Ti, and an enhanced anodic photocurrent was realized at a potential of 0 V (vs Ag/AgCl). On the basis of changes of the photocurrent signal induced by the interaction between photogenerated electrons and Cr(VI) as an effective electron scavenger in solution, a PEC sensor for Cr(VI) detection was developed and showed a linearly decreased photocurrent with increasing Cr(VI) concentration between 0.5−20 μM, 20−400 μM, and 400−1800 μM with a 0.12 μM detection limit under the optimized test conditions. The method showed simplicity, excellent selectivity and sensitivity, a wide linearity range, and high stability. The prepared PEC sensor succeeded in the Cr(VI) detection of river water and tap water samples, and it presented good applicability.