The nanostructured BiVO 4 photoanodes were prepared by electrospinning and were further characterized by XRD, SEM, and XPS, confirming the bulk and surface modification of the electrodes attained by W addition. The role of surface states (SS) during water oxidation for the asprepared photoanodes was investigated by using electrochemical, photoelectrochemical, and impedance spectroscopy measurements. An optimum 2% doping is observed in voltammetric measurements with the highest photocurrent density at 1.23 V RHE under back side illumination. It has been found that a high PEC performance requires an optimum ratio of density of surface states (N SS) with respect to the charge donor density (N d), to give both good conductivity and enough surface reactive sites. The optimum doping (2%) shows the highest N d and SS concentration, which leads to the high film conductivity and reactive sites. The reason for SS acting as reaction sites (i-SS) is suggested to be the reversible redox process of V 5+ /V 4+ in semiconductor bulk to form water oxidation intermediates through the electron trapping process. Otherwise, the irreversible surface reductive reaction of VO 2 + to VO 2+ though the electron trapping process raises the surface recombination. W doping does have an effect on the surface properties of the BiVO 4 electrode. It can tune the electron trapping process to obtain a high concentration of i-SS and less surface recombination. This work gives a further understanding for the enhancement of PEC performance caused by W doping in the field of charge transfer at the semiconductor/electrolyte interface.

Bismuth-based photocatalysts, Bi 2 WO 6 , BiVO 4 , and coupled Bi 2 WO 6 /TiO 2 −P25, have been synthesized by a facile hydrothermal method, characterized, and evaluated for the first time for the selective photooxidation of methane to methanol. Several conditions were used in order to better comprehend the reaction mechanism. The obtained BiVO 4 is, among the others, the most promising photocatalyst for this reaction, displaying higher CH 3 OH selectivity and being more stable than the others. When Bi 2 WO 6 was coupled with TiO 2 , the methane conversion increased; however, overoxidation of CH 4 to CO 2 predominates. A similar effect is observed when electron scavengers such as O 2 or Fe 3+ were introduced in the photoreactor as a result of the formation of highly oxidant radicals.

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Highly efficient Bi(2)WO(6)-TiO(2) heterostructures are synthesized by means of a hydrothermal method; they have high photoactivity for the degradation of rhodamine B under sunlike irradiation. An interesting synergetic effect between TiO(2) and Bi(2)WO(6) leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance.