Photoelectrolysis of water, also known as photoelectrochemical

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 ...

, occurs in a photoelectrochemical cell when

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

is used as the energy source for the

electrolysis In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...

of water, producing

dihydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, and ...

which can be used as a fuel. This process is one route to a "

hydrogen economy The hydrogen economy is using hydrogen to decarbonize economic sectors which are hard to electrify, essentially, the "hard-to-abate" sectors such as cement, steel, long-haul transport etc. In order to phase out fossil fuels and limit climate ch ...

", in which hydrogen fuel is produced efficiently and inexpensively from natural sources without using

fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...

s. In contrast,

steam reforming Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen product ...

usually or always uses a fossil fuel to obtain hydrogen. Photoelectrolysis is sometimes known colloquially as the ''hydrogen

holy grail The Holy Grail (french: Saint Graal, br, Graal Santel, cy, Greal Sanctaidd, kw, Gral) is a treasure that serves as an important motif in Arthurian literature. Various traditions describe the Holy Grail as a cup, dish, or stone with miracul ...

'' for its potential to yield a viable alternative to

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

as a source of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...

; such an energy source would supposedly come without the

sociopolitical Political sociology is an Interdisciplinarity, interdisciplinary field of study concerned with exploring how governance and society interact and influence one another at the micro to macro Level of analysis, levels of analysis. Interested in the ...

ly undesirable effects of extracting and using petroleum. Some researchers have practiced photoelectrolysis by means of a

nanoscale The nanoscopic scale (or nanoscale) usually refers to structures with a length scale applicable to nanotechnology, usually cited as 1–100 nanometers (nm). A nanometer is a billionth of a meter. The nanoscopic scale is (roughly speaking) a lo ...

process. Nanoscale photoelectrolysis of water could someday reach greater efficiency than that of "traditional" photoelectrolysis. Semiconductors with bandgaps smaller than 1.7 eV would ostensibly be required for efficient nanoscale photoelectrolysis using light from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. Devices based on

hydrogenase A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H2), as shown below: Hydrogen uptake () is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulfate, carbon dioxide (), and fumara ...

have also been investigated.

References

Hydrogen production Photoelectrochemistry ja:電気化学#光電気化学 {{electrochem-stub

See also

References