Zinc oxide for solar water splitting: A brief review of the material's challenges and associated opportunities

Kegel, Jan; Povey, Ian M.; Pemble, Martyn E.

doi:10.1016/j.nanoen.2018.10.043

Cited by 139 publications

(79 citation statements)

References 184 publications

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“…Semiconductors that possess attractive properties such as low cost, non-toxic, mechanically and thermally durable, high efficiency of electron-hole pairs production, low electron-hole recombination rate have been targeted as the best and most flexible for AOPs for several decades [ 10 , 11 , 12 , 13 , 14 ]. In particular, several typical compounds can be mentioned as titanium dioxide TiO 2 [ 15 , 16 ], perovskite materials ABO 3 [ 17 , 18 , 19 , 20 ], zinc oxide ZnO [ 21 , 22 ], zinc tungsten oxide ZnWO 4 [ 23 , 24 , 25 ] and so forth. However, a common feature of this semiconductor generation is the large band gap (E g ~3.2 eV) which restricts the efficiency of sunlight in stimulating photochemical reactions.…”

Section: Introductionmentioning

confidence: 99%

Fe-Doped g-C3N4: High-Performance Photocatalysts in Rhodamine B Decomposition

et al. 2020

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Herein, Fe-doped C3N4 high-performance photocatalysts, synthesized by a facile and cost effective heat stirring method, were investigated systematically using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area measurement, X-ray photoelectron (XPS), UV–Vis diffusion reflectance (DRS) and photoluminescence (PL) spectroscopy. The results showed that Fe ions incorporated into a g-C3N4 nanosheet in both +3 and +2 oxidation states and in interstitial configuration. Absorption edge shifted slightly toward the red light along with an increase of absorbance in the wavelength range of 430–570 nm. Specific surface area increased with the incorporation of Fe into g-C3N4 lattice, reaching the highest value at the sample doped with 7 mol% Fe (FeCN7). A sharp decrease in PL intensity with increasing Fe content is an indirect evidence showing that electron-hole pair recombination rate decreased. Interestingly, Fe-doped g-C3N4 nanosheets present a superior photocatalytic activity compared to pure g-C3N4 in decomposing RhB solution. FeCN7 sample exhibits the highest photocatalytic efficiency, decomposing almost completely RhB 10 ppm solution after 30 min of xenon lamp illumination with a reaction rate approximately ten times greater than that of pure g-C3N4 nanosheet. This is in an agreement with the BET measurement and photoluminescence result which shows that FeCN7 possesses the largest specific surface area and low electron-hole recombination rate. The mechanism of photocatalytic enhancement is mainly explained through the charge transfer processes related to Fe2+/Fe3+ impurity in g-C3N4 crystal lattice.

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Section: Introductionmentioning

confidence: 99%

Fe-Doped g-C3N4: High-Performance Photocatalysts in Rhodamine B Decomposition

et al. 2020

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“…12 The thermodynamically stable crystal phase of ZnO is wurtzite and, because of the electronegativity difference between the Zn and oxygen ions, the valence band of the ZnO is mainly governed by the p orbitals of oxygen, while the conduction band is controlled by either s or sp hybridized orbitals of Zn. 8,13 When ZnO is doped with Co, the Co 2+ competitively substitutes the Zn 2+ ions during growth and, thus the bandgap is narrowed by the sp-d exchange interaction between the band electrons of ZnO and the d-electrons of Co 2+ . 12,14 The applications drivers of cleaner, more efficient and viable energy sources have dened this research topic for over a decade.…”

Section: Introductionmentioning

confidence: 99%

Optical properties and carrier dynamics in Co-doped ZnO nanorods

et al. 2021

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“…The time dependence of the bandgap bleaching obtained from the FTAS is presented in Figure 4 e, Here, a faster decay of the bandgap bleaching in the Co-doped NRs and in the core–shell NRs is shown, which is attributed to alternative nonradiative decay pathways due to the introduction of a d–d transition in the bandgap by effect of the Co-doping. 35 , 36 The UV–vis stationary absorption spectra of the photoanodes are provided in Figure 4 f. These show a red-shift of the absorption bleaching in the presence of Co doping that can be attributed to strong sp–d exchange interaction 37 (see the inset in Figure 4 f). The substitution of Zn 2+ by Co 2+ leads to a stronger interaction between the sp band electrons and the localized d electrons of Co. For ZnO:Co@ZIF-8, there is an absorption red-shift compared to the other three materials, as demonstrated by the fact that ZnO:Co@ZIF-8 achieves the same absorption as ZnO, ZnO@ZIF-8, and ZnO:Co at a wavelength 15 nm higher, from 380 to 395 nm.…”

Section: Results and Discussionmentioning

confidence: 96%

Cobalt-Doped ZnO Nanorods Coated with Nanoscale Metal–Organic Framework Shells for Water-Splitting Photoanodes

Galán-González

Sivan

Hernández‐Ferrer

et al. 2020

ACS Appl. Nano Mater.

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Developing highly efficient and stable photoelectrochemical (PEC) water-splitting electrodes via inexpensive, liquid phase processing is one of the key challenges for the conversion of solar energy into hydrogen for sustainable energy production. ZnO represents one the most suitable semiconductor metal oxide alternatives because of its high electron mobility, abundance, and low cost, although its performance is limited by its lack of absorption in the visible spectrum and reduced charge separation and charge transfer efficiency. Here, we present a solution-processed water-splitting photoanode based on Co-doped ZnO nanorods (NRs) coated with a transparent functionalizing metal–organic framework (MOF). The light absorption of the ZnO NRs is engineered toward the visible region by Co-doping, while the MOF significantly improves the stability and charge separation and transfer properties of the NRs. This synergetic combination of doping and nanoscale surface functionalization boosts the current density and functional lifetime of the photoanodes while achieving an unprecedented incident photon to current efficiency (IPCE) of 75% at 350 nm, which is over 2 times that of pristine ZnO. A theoretical model and band structure for the core–shell nanostructure is provided, highlighting how this nanomaterial combination provides an attractive pathway for the design of robust and highly efficient semiconductor-based photoanodes that can be translated to other semiconducting oxide systems.

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Zinc oxide for solar water splitting: A brief review of the material's challenges and associated opportunities

Cited by 139 publications

References 184 publications

Fe-Doped g-C3N4: High-Performance Photocatalysts in Rhodamine B Decomposition

Fe-Doped g-C3N4: High-Performance Photocatalysts in Rhodamine B Decomposition

Optical properties and carrier dynamics in Co-doped ZnO nanorods

Cobalt-Doped ZnO Nanorods Coated with Nanoscale Metal–Organic Framework Shells for Water-Splitting Photoanodes

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