Regulating the Silicon/Hematite Microwire Photoanode by the Conformal Al₂O₃ Intermediate Layer for Water Splitting

Abstract

Dual-absorber photoelectrodes have been proved to possess greater potential than the single-absorber systems in the applications of photoelectrochemical (PEC) cells (e.g., solar-driven water splitting); however, the mismatching of the energy bands and substantial carrier recombinations at the two absorber interfaces are normally subsistent. Here, we introduce an intermediate layer of conformal Al2O3 into the silicon/hematite (Si/α-Fe2O3) microwire photoanode for enriching the understanding of the interaction among the interlayer, inner absorber, and outer absorber. Our results show that the Si/Al2O3/α-Fe2O3 microwire photoanode with the thickness-optimized Al2O3 can lead to a substantial increase in the photocurrent from 0.83 to 2.08 mA/cm2 at 1.23 VRHE (under 1 sun irradiation) and an obvious decrease in the onset potential relative to the counterpart without Al2O3. By analyzing the PEC responses under various monochromatic lights, PEC impedance spectroscopy, and intensity-modulated photocurrent spectroscopy, we ascribe the improvements to the fact that the suitable-thickness Al2O3 can passivate the Si microwire surfaces and the bottom surfaces of the α-Fe2O3 film and give rise to Al doping into the post-synthesized α-Fe2O3. These essential causes promote the carrier separation in α-Fe2O3, diminish the photoanode surface recombination rate, and then increase the surface charge-transfer efficiency.

Unraveling the Kinetics of Photocatalytic Water Oxidation on WO3

“…Figure a provides the typical IMPS responses of WO 3 and Cs-WO 3 . As discussed elsewhere, the semicircle of the IMPS response corresponds to the competition between surface hole transfer and surface charge recombination. , And the rate constant of surface hole transfer ( K t ) and recombination ( K r ) can be derived from the maximum radical frequency and the normalized low frequency intercept of the IMPS response in the upper quadrant (Figure S10). Figure b shows that the K t of Cs-WO 3 is smaller than that of WO 3 , which is consistent with the surface catalytic kinetics results.…”

Atomic layer deposition triggered Fe-In-S cluster and gradient energy band in ZnInS photoanode for improved oxygen evolution reaction

“…Intensity-modulated photocurrent spectroscopy (IMPS) kinetic analysis was performed to study the charge transfer and transit dynamics processes, including surface charge-transfer efficiency ( η tran ), surface charge-transfer rate constants ( K tran ), and surface charge recombination rate constants ( K rec ). The relationship between them can be described by the following formula 43 : …”

“…The frequency range is 1 kHz–0.1 Hz, and the ±5% modulation intensity is around 30 W m −2 . The Nyquist plots were used to get the rate constants of the surface charge-transfer and recombination 43 .…”

Two‐Dimentional Nanostructured Metal Oxide/Sulfide–Based Photoanode for Photoelectrochemical Water Splitting

“…This technique measures the changes of photovoltage/current in response to the varying light intensity, which is able to explore the charge dynamic relationship between incident light and the electrochemical response of the photoanode. [ 28 ] The IMPS measurement is utilized to study the surface electron transportation and recombination of PEC devices, while the IMVS measurement is used to investigate the bulk electron transportation and recombination performance. In addition, the average electron transfer time and major carrier lifetime can be calculated from IMPS/IMVS measurements.…”