Herein,
we report the cooperative effect of Zr doping and vacuum
annealing on the carrier dynamics and interfacial kinetics of anodized
TiO2 nanotubes for light-driven water oxidation. After
evaluation of different Zr loads and different annealing conditions,
it was found that both Zr doping and vacuum annealing lead to a significantly
enhanced light harvesting efficiency and photoelectrochemical performance.
The substitution of Zr4+ by Ti4+ species leads
to a higher density of surface defects such as oxygen vacancies, facilitating
electron trapping on Zr4+, which reduced the charge recombination
and hence boosted the charge transfer kinetics. More importantly,
vacuum annealing promoted the presence of surface defects. Furthermore,
the mechanistic study through impedance spectroscopy revealed that
both charge transfer and surface conductivity are significantly enhanced
due the presence of an oxygen-deficient TiO2 surface. These
results represent an important step forward in the optimization of
nanostructured TiO2-based photoelectrodes, with high potential
in photocatalytic applications, including solar fuel production.
Photoelectrochemical (PEC) catalysis offers promising strategies for sustainable development. This study demonstrated the synergistic catalytic behavior of ZrO 2 and a cobalt phosphate on anodized TiO 2 nanotubes (TNTs), which significantly enhanced the PEC performance for visible-light-driven water splitting reactions. The sequential addition of ZrO 2 /CoPi-decorated TNTs was performed via electrodeposition and photoassisted electrodeposition. The substitution of Zr 4+ by Ti 4 can lead to the creation of oxygen vacancies, enabling electron trapping, reducing charge recombination, and thereby enhancing the charge transfer efficiency. Further, in the case of TNTs/ZrO 2 /CoPi photoanode, the CoPi WOC functioned as a hole-transfer relay to promote the water-splitting reaction. Specifically, incorporating ZrO 2 /CoPi rushes the surface reaction kinetics of TNTs and considerably improves charge transfer efficiency (η CT = 90%), photocurrent density (0.86 mA/cm 2 at 1.23 V RHE ) and durability were obtained. Further, the mechanistic examination by impedance measurements showed the enhanced charge transfer, and surface conductivity for prepared materials. The proposed method can be widely used to develop electrodes made of other materials to produce solar fuels.
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