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Sunlight Generates Hydrogen through Porous Silicon

A team of Penn State mechanical engineers have come up with a way of generating hydrogen from water. This they can do by manufacturing porous silicon through a procedure that is bottom up with solar energy. The team sees this method as also applicable for biosensors, electronics that are optical and batteries.

The process of making porous silicon involves subtraction just like sculpturing whereby you remove all the unnecessary parts to remain with what is needed.

According to one Wang, silicon is of great importance thanks to its property of semi conductivity. Making porous silicon is all about etching whereby a lot of material is lost in the process. Wang together with the team make use of buildup material instead of removing by making use of a method that is chemically based.

They start it all with one of the cheapest sources of silicon and that is silicon tetrachloride. After extraction, an alloy of sodium potassium is used to treat the material. Wang also stated that the bonds between chlorine and silicon in the silicon tetrachloride are greatly strong and thus the need for a reducing agent that is equally strong. The alloy of sodium potassium thus qualifies.

The chlorine will be bound to the potassium, silicon, sodium chloride, potassium chloride and the sodium when the bonds eventually break. This bond is solid and results in a material made up of salt crystals that are in the silicon. It is then treated by heating and to remove the salt it is washed with water. The material is then left with pores whose sizes range from five to fifteen nanometers.

The whole procedure should be done in an area free from oxygen in the air. The researchers conducted this procedure in an atmosphere that is filled with argon. This is because of the alloy for sodium potassium is very reactive.

Wang believes the scaling can be done to the process up to the manufacturing level since there are processes at industrial scales that make use of the sodium potassium alloy therefore they can adopt the same to make this new kind of silicon.

Due to numerous pores on the silicon particles, the surface area is large and can be used as a catalyst when the sun shines on water and the porous silicon. It is the sun’s energy that excites the electron which will reduce water and generate hydrogen in gaseous form.

Keywords: nanotechonology,porous silicon


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