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

Abstract

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 (N d), 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.

Efficient sensitization of CdTe QDs towards PTCDA for sensitive photoelectrochemical Hg2+ assay

“…Cadmium telluride quantum dots (CdTe QDs) with numerous surface states are equipped with desirable properties such as tunable size, low bandgap energy, and high light trapping ability. 21 Notably, the band gap of CdTe QDs is 1.80 eV with the valence band (VB) and conduction band (CB) gaps of 0.770 eV and −1.03 eV, respectively. 22 The band gap of PTCDA is 2.50 eV with the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of −0.210 eV and 2.29 eV, respectively.…”

Enhanced Photoelectrochemical Response of the ZnO/V2O5 Heterojunction Via Improved Visible-Light Absorption and Charge Carrier Separation

“…The first metal oxide semiconductor for PEC water splitting was a TiO 2 photo-anode, as demonstrated by Fujishima and Honda in 1972 . A wide range of single semiconductor metal oxides, such as ZnO, TiO 2 , WO 3 , BiVO 4 , Fe 2 O 3 , etc., have been reported as photo-electrode materials in PEC water splitting because of their good optical and electrical properties, suitable band alignment with water redox potential (O 2 /H 2 O), and low cost. Among these, ZnO is an n-type wide band gap semiconductor (∼3.2 eV) that has been widely studied for PEC water splitting because it has higher electron mobility than TiO 2 to suppress the electron–hole recombination rate and has good photocorrosion stability.…”

Enhanced Charge Separation and Transfer by BiVO4 Heterojunction and N-Doped for TiO2 Nanotubes during Photoelectrochemical Water Splitting

“…23 After the successful construction of heterojunction structures, the photoanodes with heterojunction formation could enlarge the solar light absorption, enhance the charge carrier injection, and facilitate the enhanced separation of electron−hole pairs. 42 Once the solar light is illuminated on the TiO 2 photoanode, the electrons from the conduction band of TiO 2 and the electrons transferred from the heterojunction could be transported to the other electrode by the external circuit to participate in the hydrogen evolution reaction. In numerous narrow band gap semiconductors, BiVO 4 has been greatly researched as a narrow band gap semiconductor in recent years due to its attractive band structure and suitable band gap energy.…”

“…That could enhance the solar light absorption and the PEC property . After the successful construction of heterojunction structures, the photoanodes with heterojunction formation could enlarge the solar light absorption, enhance the charge carrier injection, and facilitate the enhanced separation of electron–hole pairs . Once the solar light is illuminated on the TiO 2 photoanode, the electrons from the conduction band of TiO 2 and the electrons transferred from the heterojunction could be transported to the other electrode by the external circuit to participate in the hydrogen evolution reaction.…”