Progress in semiconductor materials for photocathodic protection: Design strategies and applications in marine corrosion protection

Photochargeable Semiconductors: in “Dark Photocatalysis” and Beyond

“…TiO 2 /WO 3 heterojunctions are the first choice when it comes to photocathodic protection with long-term activity in the dark. [85,90] In general, the heterojunction approach consists of a light-absorbing semiconductor (TiO 2 being the state of the art) coupled to an electron pool. Electrons are photogenerated in the former and then transferred to the latter when they reside for a sufficiently long time (Figure 10c).…”

“…Although several examples of Ti-based semiconductors for light-assisted anti-corrosion followed, [89] the interest in intrinsic energy-storing photoanodes for cathodic protection has flourished in the past few years. [85,90] Actually, the first example of energy-storing photoanodes for anticorrosion was proposed as early as 2001. [91] There, when stainless steel was coated with a TiO 2 /WO 3 composite, the open circuit [86] Copyright 2002.…”

Review of TiO2-Based Heterojunction Coatings in Photocathodic Protection

“…TiO 2 is often studied due to its excellent stability and nonconsumption properties . However, its E g is about 3.2 eV, which is not conducive to absorbing visible light, and a single semiconductor is inadequate for the effective separation of e – –h + . Studies have demonstrated that constructing TiO 2 -based heterojunction coatings can effectively solve these problems.…”

“…31 However, its E g is about 3.2 eV, which is not conducive to absorbing visible light, and a single semiconductor is inadequate for the effective separation of e − −h + . 32 Studies have demonstrated that constructing TiO 2 -based heterojunction coatings can effectively solve these problems. On the one hand, heterojunction coatings greatly expand the light absorption range, and, on the other hand, they facilitate the efficient separation of e − −h + , therefore enhancing the PCP performance.…”

Review on the Solar-Driven Photocathodic Protection of Metals in the Marine Environment

“…There are two forms of PCP technology in application. One is to coat the semiconductor on the exterior of the safeguarded metal [7], and the other is to connect the semiconductor material to the protected metal as a photoanode [8][9][10]. Under solar light irradiation, when the energy provided by the natural light (hv) is larger than the forbidden bandwidth of the photoanode, the electrons situated in the valence band (VB) will absorb the energy from photons and undergo excitation to jump to the conduction band (CB), producing photogenerated electrons (e − ) and photogenerated holes (h + ).…”