Monolayer Nano Tungsten Disulfide Can Provide Better Capture of Solar Energy

Electrolysis is the cleanest way to produce hydrogen, but because it requires a lot of electricity and expensive catalysts (such as platinum), it is expensive. For this reason, most of the hydrogen produced by developed countries in the world is made from natural gas through a process called steam reforming. Although it is cheaper, it also produces greenhouse gas carbon dioxide. Moreover, China is not a big country with natural gas reserves. In addition, platinum metal is not only precious, but also produces toxic by-products. Therefore, searching for hydrogen evolution materials with low overpotential, low cost, high earth content and large-scale synthesis is the goal that scientists focus on.

Recently, scientists are studying a new material, low-cost electrochemical catalyst, which can generate and store more energy from the sun. It can reduce the cost of hydrogen production by using solar energy or other clean energy, so that the clean energy of hydrogen electrolysis can be popularized. The catalyst is based on two-dimensional monolayer nano tungsten disulfide.

Since the discovery of graphene in 2004, material science has changed dramatically. Graphene has the advantage of high conductivity. However, graphene is a zero band gap material, and it is difficult to do much in the field of electrolytic hydrogen. Therefore, transition metal two-dimensional materials (TMDs), such as tungsten disulfide and molybdenum disulfide, have attracted wide interest.

Tungsten disulfide, a crystalline material, tends to form thin sheets of three-atom thickness. The electricity generated by renewable energy sources such as solar cells or wind turbines can be transferred to tungsten sulfide sheets through conductive support materials. Current flows to the catalytic edge of the sheet, where it is transferred to water and eventually splits into oxygen and hydrogen. Therefore, monolayer nano tungsten disulfide is a good material to replace precious metal for hydrogen electrolysis.

The team is analysing how to transfer electricity from auxiliary materials to tungsten disulfide sheets. Tungsten disulfide is synthesized into sheets perpendicular to the surface, such as blades in radiators or tubes protruding from the surface. In the two configurations, the edge of the sheet is directed to the supporting material, and the single layer nano tungsten disulfide has better hydrogen evolution performance and lower overpotential. When the overpotential of hydrogen evolution is 200 mV, the current density is 2.53 mA/cm²; when the overpotential is 300 mV, the current density can reach 32 mA/cm². Its performance is close to that of platinum, and its photoelectric stability is very high, but the cost is much cheaper, which also provides a favorable guarantee for the continuous photoelectric decomposition of seawater to produce hydrogen.

Water is decomposed into hydrogen and oxygen molecules by electrolytic catalytic materials, which can be stored and then recombined into fuel cells, which can be used in new energy vehicles.

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