Elucidating the electronic structure of CuWO₄ thin films for enhanced photoelectrochemical water splitting

Abstract

CuWO4 is an n-type oxide semiconductor with a bandgap of 2.2 eV which exhibits great potential for photoelectrochemical (PEC) conversion of solar energy into chemical fuels.

Femtosecond Charge Density Modulations in Photoexcited CuWO4

“…As mentioned above, the electronic structure of CuWO 4 is still an open question and there have been models suggested by several authors. For instance, Tian et al 8 reported that the bottom of the conduction band of CuWO 4 comes from Cu 3d orbitals while the top of the valence band is formed by Cu 3d orbitals and O 2p orbitals. Hoang et al 14 pointed out that O 2p orbitals are dominant in the valence band of CuWO 4 while its conduction band is formed mainly by Cu 3d orbitals and W 5d orbitals.…”

“… 7 It is known as an n-type semiconductor and its valence band is believed to be composed mainly of oxygen 2p states that are hybridized with tungsten and copper s, p, and d states. 8 , 9 The conduction band contains mainly W 5d states hybridized with the oxygen 2p states. In addition, it has been claimed that the single Cu 3d hole contributes to the bottom of the conduction band, which shifts the conduction band minimum in CuWO 4 downward compared to WO 3 .…”

“… 10 − 14 However, the origin of charge carriers and their behavior in CuWO 4 are not well understood due to the scarcity of the experimental studies that probe the relaxation dynamics of the optically excited Cu electronic states, particularly in the fs/ps time domain. 15 , 16 Therefore, we believe that understanding the ultrafast electronic transitions in CuWO 4 in this time domain could provide a clearer insight on the nature of the electronic structure of CuWO 4 , which is highly debatable in literature 8 , 10 , 11 , 14 , 17 …”

“…The optical laser excitation triggers a transition from the oxygen 2p valence band to the W 5d conduction band. 8 The empty Cu 3d state is not active in the optical transition and, as such, plays the role of a spectator state. During the X-ray excitation process, an electron is excited to the Cu 3d band and one can observe its reaction to the optical excitation.…”

Effects of porous activated carbon on TiO2 photo‐activity for high concentration 2,4‐DCP degradation as environmental remediation

“…19 Nonetheless, the progression of adsorption method is slow and time consuming and necessitates a huge amount of adsorbent for operative environmental remediation. [20][21][22] In recent years, photo-catalytic technology has received more and more attention due to its high efficiency, low cost, and environmental friendliness. 23,24 However, the photocatalytic activity of photo-catalytic technology for high concentrations of pollutants is still insufficient.…”