Imperfect makes perfect: defect engineering of photoelectrodes towards efficient photoelectrochemical water splitting

Abstract

Photoelectrochemical (PEC) water splitting for hydrogen evolution has been considered as a promising technology to solve the energy and environmental issues. However, the solar-to-hydrogen (STH) conversion efficiencies of current PEC...

Structural, optical, and dielectric properties of hydrothermally synthesized SnO2 nanoparticles, Cu/SnO2, and Fe/SnO2 nanocomposites

“…The presence of more than one valence state for the host lattice suggests polar-ionic conduction due to e-hopping [31]. Materials in the nanoscale exhibit localized electronic states at the Fermi level due to their small grain sizes, which enable carriers to carry electricity while hopping between occupied and unoccupied localized states [32]. The mentioned mechanism is mainly controlled by the density of states and Fermi level position and the latter is significantly affected by interior defects [33,34].…”

Enhancing the PEC Efficiency in the Perspective of Crystal Facet Engineering and Modulation of Surfaces

“…As discussed earlier, BiVO 4 , Fe 2 O 3 , and WO 3 are among the most researched photoanodes and several cocatalysts have been designed to facilitate the charge transfer process involving these anodes. In this context, several transition metal oxides, layered oxyhydroxides, metal–organic framework derived oxides have been used as cocatalysts. − …”

“…The average lifetime and the mean diffusion length of any material is intrinsic to the material, but manipulation of the morphology can reduce the recombination and thus enhance the diffusion length of the charge carrier. Moreover, the engineered surface morphology enhances the effective surface area of the photoelectrode, increases the number of catalytic sites on the surface, accelerates interfacial charge transfer, enhances light absorption, and reduces charge carrier trapped surface states. − Important investigations and reports are available on surface morphology dictated improvements in the photocurrent generation efficiency. Su et al synthesized WO 3 photoanodes with both nanowire and nanoflake morphologies through the solvothermal method; the results are shown in Figure .…”

“…The surface defects also act as the adsorption centers of reactive species. However, at higher defect concentrations the defects might act as the centers of charge recombination, which is detrimental to the PEC performance …”

“…However, at higher defect concentrations the defects might act as the centers of charge recombination, which is detrimental to the PEC performance. 59 Hematite photoanode is very promising in terms of fulfilling the requirements of the band gap (2.1 eV), allowing it to absorb a significant portion of the solar spectrum. However, the surface trap states limit the performance by acting as centers for electron−hole (e−h) recombination and are also responsible for high overpotentials.…”