Designing robust anatase-branch@hydrogenated-rutile-nanorod TiO2 as accurate and sensitive photoelectrochemical sensors

It is of great significance to design a simple, robust, rapid, and sensitive method for detecting chemical oxygen demand (COD) in wastewater. A photoelectrochemical COD sensor based on linear photocurrent-concentration analytical principle has attracted tremendous attention in the on-site determination of COD. However, insufficient accuracy, linear range, and short lifetime have been the major challenges impeding the commercialization of this analytical method for COD testing. To overcome these challenges, a high-performance anatasebranch@hydrogenated rutile-nanorod TiO2 (AB@H-RTNR) photoelectrode is fabricated. The as-prepared photoanodes successfully achieved sensitive determination of COD with a detection limit of 0.2 ppm (S/N = 3), an RSD% of 1.5 %, a wide linear detection range of 1.25-576 ppm and an average recovery rate fluctuating between 100 % +/- 4 % for artificial wastewater sample analyses. Such performances are outstanding in comparison with the standard COD method. Furthermore, the AB@H-RTNR photoelectrode has a long lifetime, e.g., each electrode is capable of ca. 3000 measurements. The favorable performance of AB@H-RTNR can be attributed to the adoption of the in-situ growth method of TiO2 nanostructure and the oxygen vacancies in crystal lattice generated by the hydrogenation process. The result suggests that the as-prepared AB@H-RTNR has overcome the barriers for practical application and final commercialization of this photocurrent-based PeCOD technology.