Bismuth vanadate is the
inorganic compound with the formula BiVO
4. It is a bright yellow solid. It is widely studied as visible light photo-catalyst with a narrow band gap of less than 2.4 eV. It is a representative of "complex inorganic colored pigments," or CICPs. More specifically, bismuth vanadate is a mixed-
metal oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
. Bismuth vanadate is also known under the
Colour Index International
Colour Index International is a reference database jointly maintained by the Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists. It currently contains over 27,000 individual products listed under 13, ...
as C.I. Pigment Yellow 184.
[B. Gunter "Inorganic Colored Pigments” in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012.] It occurs naturally as the rare minerals pucherite, clinobisvanite, and dreyerite.
History and uses
Bismuth vanadate is a bright yellow powder and may have a slight green tint. When used as a pigment it contains a high Chroma and excellent hiding power. In nature, bismuth vanadate can be found as the mineral pucherite, clinobisvanite, and dreyerite depending on the particular polymorph formed. Its synthesis was first recorded in a pharmaceutical patent in 1924 and began to be used readily as a pigment in the mid-1980s. Today it is manufactured across the world for pigment use.
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Properties
Most commercial bismuth vanadate pigments are based on monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...
(clinobisvanite) and tetragonal
In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...
(dreyerite) structures though in the past two phase systems involving a 4:3 relationship between bismuth vanadate and bismuth molybdate (Bi2MoO6) have been used.
As a photocatalyst
BiVO4 has received much attention as a photocatalyst for water splitting
Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen:
:2 H2O → 2 H2 + O2
Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy, base ...
and for remediation.
In the monoclinic phase, BiVO4 is an n-type photoactive semiconductor with a bandgap of 2.4 eV, which has been investigated for water splitting after doping with W and Mo.
Production
While most CICPs are formed exclusively through high temperature calcination
Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), gener ...
, bismuth vanadate can be formed from a series of pH controlled precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
reactions. These reactions can be carried out with or without the presence of molybdenum depending on the desired final phase. It is also possible to start with the parent oxides (Bi2O3 and V2O5) and perform a high temperature calcination to achieve a pure product.[Sulivan, R. European Patent Application 91810033.0, 1991.]
References
{{Bismuth compounds
Vanadates
Bismuth compounds