Efficient and Stable Photoelectrochemical Seawater Splitting with TiO2@g-C3N4 Nanorod Arrays Decorated by Co-Pi

Co-Pi decorated TiO2@graphitic carbon nitrides (g-C3N4) nanorod arrays (denoted as CCNRs) with different mass ratios of g-C3N4 have been constructed on the FTO substrate through three processes, hydrothermal growth, chemical bath deposition and electrodeposition. First, TiO2 nanorod arrays were grown onto a FTO substrate by a hydrothermal method. Second, g-C3N4 was coated onto the TiO2 nanorod arrays by immersing the above substrate with TiO2 nanorod arrays into a solution of urea and then heated at higher temperature. In this procedure, the amount of the g-C3N4 on the TiO2 nanorod arrays can be controlled by tuning the concentration of the urea solution. At last, Co-Pi were decorated on the surface of the TiO2@g-C3N4 by electrodeposition. The as-prepared CCNRs were characterized by XRD, FESEM, TEM, XPS, UV–vis, and FTIR, respectively, which illustrated that Co-Pi moieties were successfully decorated on the hybrid TiO2@g-C3N4 nanorod arrays. Photoelectrochemical (PEC) measurements have demonstrated that the prepared CCNRs serve as an efficient and stable photoanode for PEC seawater splitting. The photocurrent density reaches 1.6 mA/cm2 under 100 mW/cm2 (AM1.5G) light illumination at 1.23 V (RHE). More significantly, the CCNRs photoanode is quite stable during seawater splitting and the performance remain undiminished even after 10 h continuous illumination. Finally, a systematical photocatalytic mechanism of the Co-Pi decorated TiO2@g-C3N4 was proposed, and it can be considered as potential explanation of enhanced PEC performance.