Energy Band Engineering by CdTe/Si Codoped TiO₂ Nanoarrays for Enhanced Photoelectrochemical Water Splitting

The wide bandgap energy of TiO2 limited its photocatalytic activity to UV light. To meet this challenge, TiO2 nanorods were doped with Si atoms and decorated by CdTe QDs to enhance the electronic structure, broaden the absorption domain, and improve photoelectrochemical (PEC) water splitting. Incorporation of Si atoms in the TiO2 structure effectively enhanced the transfer of charge carriers and the wettability of the surface in the Si:TiO2 electrode and made it an effective platform for solar-assisted water splitting. Moreover, the IPCE results prove that CdTe QDs with high absorption coefficient and photon upconversion spread the photoresponse of CdTe/Si:TiO2 to visible light with an improved photocurrent density of 4.3 mA cm–2 at the potential of 1.23 V vs RHE. The excellent increase of 12.5 times in PEC activity of CdTe/Si:TiO2 electrode as compared to unmodified TiO2 nanoarrays and its low overpotential are due to the faster electron transfer kinetics, enhanced charge carriers density (Nd), and reduced charge recombination rate. The photocurrent stability of CdTe/Si:TiO2 in numerous on/off cycles and its long-term durability with a photocurrent decay of about 5% over 10 h show its high photocorrosion resistance. The current study signifies that CdTe/Si:TiO2 is a suitable and highly efficient photoelectrocatalyst for water splitting.