Oxygen vacancies (OVs) are a mixed blessing for the photoelectrochemical (PEC) water oxidation performance of monoclinic tungsten trioxide (m-WO 3 ) photoanodes. Although it is widely accepted that a moderate concentration of OVs is beneficial for the PEC performance of the m-WO 3 photoanodes, this argument assumes a uniform distribution of OVs throughout the m-WO 3 crystal. In this case, only the overall concentration of OVs needs to be considered. However, the spatial non-uniformity of OV defects in m-WO 3 photoanodes has not been thoroughly examined. In this study, by employing a m-WO 3 nanorod array as a model photoanode, the aim is to show that a higher OV concentration near the surface of m-WO 3 compared to that in the bulk is advantageous for the PEC performances of this material. In addition, a laser-assisted defect control (LADC) process is employed to manipulate the spatial distribution of OVs in the m-WO 3 photoanodes to achieve enhanced PEC performances. Moreover, a one-step laser deposition process is introduced to obtain an ultrathin FeNi oxygen evolution catalyst overlayer on the defect-controlled m-WO 3 photoanodes, further improving PEC performance, photostability, and Faradaic efficiency.
Generally, a high-temperature postannealing
process is required
to enhance the photoelectrochemical (PEC) performance of hematite
nanorod (NR) photoanodes. However, the thermal annealing time is limited
to a short duration as thermal annealing at high temperatures can
result in some critical problems, such as conductivity degradation
of the fluorine-doped tin oxide film and deformation of the glass
substrate. In this study, selective laser processing is introduced
for hematite-based PEC cells as an alternative annealing process.
The developed laser-induced phase transformation (LIPT) process yields
hematite NRs with enhanced optical, chemical, and electrical properties
for application in hematite NR-based PEC cells. Owing to its improved
properties, the LIPT-processed hematite NR PEC cell exhibits an enhanced
water oxidation performance compared to that processed by the conventional
annealing process. As the LIPT process is conducted under ambient
conditions, it would be an excellent alternative annealing technique
for heat-sensitive flexible substrates in the future.
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