Two Principles
Two Principles
Two Principles
Hematite structure
Researchers have extensively investigated the use of
hematite (α-Fe2O3) in PEC water-splitting devices due to
its low cost, ability to be n-type doped, and band gap
(2.2eV). However, performance is plagued by poor
conductivity and crystal anisotropy. [21] Some researchers
have enhanced catalytic activity by forming a layer of co-
catalysts on the surface. Co-catalysts include cobalt-
phosphate[22] and iridium oxide,[23] which is known to be a
highly active catalyst for the oxygen evolution reaction. [20]
Tungsten oxide[edit]
Tungsten(VI) oxide (WO3), which exhibits several different
polymorphs at various temperatures, is of interest due to
its high conductivity but has a relatively wide, indirect
band gap (~2.7 eV) which means it cannot absorb most of
the solar spectrum. Though many attempts have been
made to increase absorption, they result in poor
conductivity and thus WO3 does not appear to be a viable
material for PEC water splitting. [20]
Bismuth vanadate[edit]
With a narrower, direct band gap (2.4 eV) and proper
band alignment with water oxidation potential, the
monoclinic form of BiVO
[20]
4 has garnered interest from researchers. Over time, it
has been shown that V-rich and compact films[25] are
[24]