Research
Research is being conducted over photocatalysis, the acceleration of a photoreaction in the presence of a catalyst. Its comprehension has been made possible ever since the discovery of water electrolysis by means of the titanium dioxide. Artificial photosynthesis is a research field that attempts 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 chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other chemicals are recycled. The iron oxide process requires an efficient source of heat.
The sulfur-iodine cycle (S-I cycle) is a series of thermochemical processes used to produce hydrogen. The S-I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other chemicals are recycled. The S-I process requires an efficient source of heat.
More than 352 thermochemical cycles have been described for water splitting or thermolysis., These cycles promise to produce hydrogen oxygen from water and heat without using electricity. Since all the input energy for such processes is heat, they can be more efficient than high-temperature electrolysis. This is because the efficiency of electricity production is inherently limited. Thermochemical production of hydrogen using chemical energy from coal or natural gas is generally not considered, because the direct chemical path is more efficient.
For all the thermochemical processes, the summary reaction is that of the decomposition of water:
All other reagents are recycled. None of the thermochemical hydrogen production processes have been demonstrated at production levels, although several have been demonstrated in laboratories.
There is also research into the viability of nanoparticles and catalysts to lower the temperature at which water splits.
Research is concentrated on the following cycles :
| Thermochemical cycle | LHV Efficiency | Temperature (°C/F) |
|---|---|---|
| Cerium(IV) oxide-cerium(III) oxide cycle (CeO2/Ce2O3) | ? % | 2,000 °C (3,630 °F) |
| Hybrid sulfur cycle (HyS) | 43 % | 900 °C (1,650 °F) |
| Sulfur iodine cycle (S-I cycle) | 38 % | 900 °C (1,650 °F) |
| Cadmium sulfate cycle | 46 % | 1,000 °C (1,830 °F) |
| Barium sulfate cycle | 39 % | 1,000 °C (1,830 °F) |
| Manganese sulfate cycle | 35 % | 1,100 °C (2,010 °F) |
| Zinc zinc-oxide cycle (Zn/ZnO) | 44 % | 1,900 °C (3,450 °F) |
| Hybrid cadmium cycle | 42 % | 1,600 °C (2,910 °F) |
| Cadmium carbonate cycle | 43 % | 1,600 °C (2,910 °F) |
| Iron oxide cycle (Fe3O4/FeO) | 42 % | 2,200 °C (3,990 °F) |
| Sodium manganese cycle | 49 % | 1,560 °C (2,840 °F) |
| Nickel manganese ferrite cycle | 43 % | 1,800 °C (3,270 °F) |
| Zinc manganese ferrite cycle | 43 % | 1,800 °C (3,270 °F) |
| Copper-chlorine cycle (Cu-Cl) | 41 % | 550 °C (1,022 °F) |
Read more about this topic: Water Splitting
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