Water splitting to replicate the natural process of photosynthesis, converting sunlight, water and carbon dioxide into carbohydrates and oxygen. Recently, this has been successful in splitting water into hydrogen and oxygen using an artificial compound called Nafion. High-temperature electrolysis (also HTE or steam electrolysis) is a method currently being investigated for the production of hydrogen from water with oxygen as a by-product. Other research includes thermolysis on defective carbon substrates, thus making hydrogen production possible at temperatures just under 1000 °C. The iron oxide cycle is a series of thermochemical processes used to produce hydrogen. The iron oxide cycle consists of two
Carbon dioxide standard hydrogen electrode. The nickel-containing enzyme carbon monoxide dehydrogenase catalyses this process. Carbon dioxide is colorless. At low concentrations the gas is odorless; however, at sufficiently-high concentrations, it has a sharp, acidic odor. At standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m, about 1.67 times that of air. Carbon dioxide has no liquid state at pressures below . At 1 atmosphere (near mean sea level pressure), the gas deposits directly to a solid at temperatures below and the solid sublimes directly to a gas above −78.5 °C. In its solid state, carbon dioxide is commonly