Hematite‐Based Water Splitting with Low Turn‐On Voltages

Du, Chun; Yang, Xiaogang; Mayer, Matthew T.; Hoyt, Henry; Xie, Jin; McMahon, Greg; Bischoping, Gregory; Wang, Dunwei

doi:10.1002/anie.201306263

Cited by 416 publications

(399 citation statements)

References 29 publications

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“…Some demonstrated techniques for evaluating the interplay between these mechanisms include transient absorption spectroscopy, 100 impedance spectroscopy and transient photocurrent spectroscopy, 26 and photovoltage measurements. 58,101 In a "well" designed system ( Fig. 8a and b), there will be passivated surface trap states, a fast interfacial charge-transfer rate for water splitting, and a very slow rate of photocorrosion.…”

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confidence: 99%

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Zheng

Spurgeon

et al. 2014

Energy Environ. Sci.

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An important approach for solving the world's sustainable energy challenges is the conversion of solar energy to chemical fuels. Semiconductors can be used to convert/store solar energy to chemical bonds in an energy-dense fuel. Photoelectrochemical (PEC) water-splitting cells, with semiconductor electrodes, use sunlight and water to generate hydrogen. Herein, recent studies on improving the efficiency of semiconductor-based solar water-splitting devices by the introduction of surface passivation layers are reviewed. We show that passivation layers have been used as an effective strategy to improve the charge-separation and transfer processes across semiconductor-liquid interfaces, and thereby increase overall solar energy conversion efficiencies. We also summarize the demonstrated passivation effects brought by these thin layers, which include reducing charge recombination at surface states, increasing the reaction kinetics, and protecting the semiconductor from chemical corrosion.These benefits of passivation layers play a crucial role in achieving highly efficient water-splitting devices in the near future. Broader contextSemiconductor interface is one of the most important components/regions in photoelectrochemical (PEC) water splitting devices. The serious surface charge recombination, slow charge transfer kinetics and the poor photoelectrochemical stability are the three main challenges for the practical PEC water splitting devices. Recently, the studies of constructing passivation layer onto the semiconductor to address these challenges have attracted increasing research attentions, due to the potential application of solar to chemical energy conversion. When these layers incorporated onto semiconductor surface, signicant changes of the interface would be found including charge transfer improvement, surface charge recombination, and chemical corrosion, etc. Although various strategies have been suggested for this surface modication, a synergetic effect must be achieved on an advanced photoelectrodes accounting for the improved solar-tohydrogen efficiencies. This review will shed light on the recent PEC water splitting work surface state passivation, corrosion retardation and charge transfer improvement in this passivation layer.

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confidence: 99%

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Zheng

Spurgeon

et al. 2014

Energy Environ. Sci.

Self Cite

554

439

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“…Recent work reported that the onset potential of hematite can be drastically reduced to 0.62 V vs. RHE though loading a Ni-based catalyst, but the intrinsic onset potential of the hematite electrodes is 1.0 V vs. RHE. 18 Up to now, the preparation of hematite with intrinsically low onset potential has remained a great challenge.Herein we report a hematite photoanode with an intrinsic onset potential of as low as 0.58 V vs. RHE for PEC water oxidation. The passivation of the surface state and the gradient structure of the hematite photoanode using H 2 -O 2 flame treatment at high temperature are supposed to suppress surface charge recombination and promote the interfacial charge transfer, resulting in this low onset potential.…”

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confidence: 99%

A hematite photoanode with gradient structure shows an unprecedentedly low onset potential for photoelectrochemical water oxidation

Han

Zong

Wang

et al. 2014

Phys. Chem. Chem. Phys.

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Ultra-high onset potential hinders the application of hematite for photoelectrochemical (PEC) water splitting. Herein, a hematite photoanode with an unprecedentedly low onset potential of 0.50 V vs. the reversible hydrogen electrode for PEC water oxidation is reported. The drastically reduced onset potential is mainly ascribed to the passivation of the hematite surface states and the gradient structure made by H2-O2 flame at high temperature.

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“…Electronic surface states of photoelectrodes could cause a degree of the so-called Fermi level pining [65]. The accumulation of positive charges occurring at the photoanode/water interface at low bias potentials was found to be at its maximum when the photocurrent of photoanode onsets, thus possibly reducing or even canceling the effects of the space charge layer, and the potential drop occurs over the Helmholtz layer instead of in the photoelectrodes [10,66,67]. Under this condition, the holes captured by the surface states with energy within the band gap cannot drive the water oxidation reaction effectively; the surface states would then become the recombination sites for electrons and hole.…”

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confidence: 96%