Tailoring the Electronic Band Gap and Band Edge Positions in the C2N Monolayer by P and As Substitution for Photocatalytic Water Splitting
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Exploiting earth-abundant and low-cost photocatalysts for high efficiency photocatalytic water splitting is of profound significance. Herein, we report an improved photocatalytic water splitting activity by P and As substitution at the N-site in the C2N monolayer using state-of-the-art hybrid density functional calculations. Our results show that the band gap can be reduced in C2N by increasing the concentrations of P and As substitution, and at the same time the obtained band gap value is higher than the free energy of water splitting except for As with concentrations of x = 0.333. This indicates that these new compositions of P/As substituted C2N monolayers are thermodynamically suitable to drive hydrogen evolution reaction. The calculated effective mass of charge carriers illustrates that charge transfer to the reactive sites would be easier in the substituted system than the pure C2N, and also our results suggest that the recombination rate would be lower in the substituted system, indicating the enhancement in the efficiencies of photocatalytic water splitting. The band edge position with respect to the redox potentials of water shows that P/As substituted C2N monolayers are the potential photocatalysts for water splitting than the pristine C2N monolayer. From the optical absorption spectra, we found that P/As substituted C2N monolayer shows optical absorption extended more into the visible region, indicating enhanced energy harvesting. Our results reflect that the P/As substituted C2N monolayer could be the potential visible-light photocatalyst for overall water splitting.Keywords:
Photocatalytic water splitting
Absorption edge
Visible spectrum
Charge carrier
Photocatalytic water splitting
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Photocatalytic water splitting has been widely studied as a means of converting solar energy into hydrogen as an ideal energy carrier in the future. Systems for photocatalytic water splitting can be divided into one-step excitation and two-step excitation processes. The former uses a single photocatalyst while the latter uses a pair of photocatalysts to separately generate hydrogen and oxygen. Significant progress has been made in each type of photocatalytic water splitting system in recent years, although improving the solar-to-hydrogen energy conversion efficiency and constructing practical technologies remain important tasks. This perspective summarizes recent advances in the field of photocatalytic overall water splitting, with a focus on the design of photocatalysts, co-catalysts and reaction systems. The associated challenges and potential approaches to practical solar hydrogen production via photocatalytic water splitting are also presented.
Photocatalytic water splitting
Energy transformation
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Photocatalytic water splitting
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Photocatalytic overall water splitting into H2 and O2 is expected to be a promising method for the efficient utilization of solar energy. The design of optimal photocatalyst structures is a key to efficient overall water splitting, and the development of photocatalysts which can efficiently convert large portion of visible light spectrum has been required. Recently, a series of complex perovskite type transition metal oxynitrides, LaMgxT 1-xO1+3xN2-3x, was developed as photocatalysts for direct water splitting operable at wide wavelength of visible light. In addition two-step excitation water splitting via a novel photocatalytic device termed as photocatalyst sheet was developed. This consists of two types of semiconductors (hydrogen evolution photocatalyst and oxygen evolution photocatalyst) particles embedded in a conductive layer, and showed high efficiency for overall water splitting. These recent advances in photocatalytic water splitting were introduced.
Photocatalytic water splitting
Visible spectrum
Oxygen evolution
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Defect-rich 1D TiO2nanostructures show excellent photoelectrochemical water splitting property in the visible light region with a low onset potential of 0.3 Vvs. RHE and a remarkably high conversion efficiency of 3.6%.
Visible spectrum
Photoelectrochemistry
Energy transformation
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With a view to the particularity of overall water splitting,the preparation of photocatalytic materials and their performance for hydrogen and oxygen production from overall water splitting are reviewed in relation to the design of structure and energy band of photocatalytic materials as well as their surface modification.The principle of two step reaction(Z system) for overall water splitting and several currently available Z systems are introduced.Furthermore,existing problems of photocatalytic overall water splitting are also briefed.
Photocatalytic water splitting
Oxygen evolution
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Photocatalytic water splitting
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Exploiting earth-abundant and low-cost photocatalysts for high efficiency photocatalytic water splitting is of profound significance. Herein, we report an improved photocatalytic water splitting activity by P and As substitution at the N-site in the C2N monolayer using state-of-the-art hybrid density functional calculations. Our results show that the band gap can be reduced in C2N by increasing the concentrations of P and As substitution, and at the same time the obtained band gap value is higher than the free energy of water splitting except for As with concentrations of x = 0.333. This indicates that these new compositions of P/As substituted C2N monolayers are thermodynamically suitable to drive hydrogen evolution reaction. The calculated effective mass of charge carriers illustrates that charge transfer to the reactive sites would be easier in the substituted system than the pure C2N, and also our results suggest that the recombination rate would be lower in the substituted system, indicating the enhancement in the efficiencies of photocatalytic water splitting. The band edge position with respect to the redox potentials of water shows that P/As substituted C2N monolayers are the potential photocatalysts for water splitting than the pristine C2N monolayer. From the optical absorption spectra, we found that P/As substituted C2N monolayer shows optical absorption extended more into the visible region, indicating enhanced energy harvesting. Our results reflect that the P/As substituted C2N monolayer could be the potential visible-light photocatalyst for overall water splitting.
Photocatalytic water splitting
Absorption edge
Visible spectrum
Charge carrier
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Water splitting into hydrogen and oxygen using oxide semiconductors photocatalytic under visible light irradiation is an attractive research field.But the problems is that the photocatalysts which have found are not active and yet stable under visible light irradiation.So finding out a new types catalysts under visible irradiation is necessary.This paper intends to introduce the latest progress in the field,and some mechanisms of photocatalysts splitting water under visible irradiation.
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Photocatalytic water splitting
Visible spectrum
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