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

Abstract

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.