Tapping sun’s light and heat to make hydrogen

Environmentally friendly fuel cells may someday power most cars, homes, and industries. Yet the energy they supply won’t be all that clean if the hydrogen that the fuel cells consume derives from fossil fuels. So says Stuart Licht of the University of Massachusetts in Boston, who leads a U.S.–Israeli team of researchers that has demonstrated a new solar-powered way to produce hydrogen from water.

Typically in solar-based electricity generation, only a fraction of the sun’s visible and ultraviolet light produces electrons with sufficient energy to split water into hydrogen and oxygen. In the new method, the researchers first use the sun’s infrared radiation to heat molten sodium hydroxide mixed with water to oven temperatures that prime the water molecules to break apart.

Under these conditions, even electrons with too little energy to split water molecules at ambient temperatures cleave the heated ones. Thus, hydrogen could be produced using widely available silicon photovoltaic cells, Licht says.

In the Dec. 8, 2003 Chemical Communications, Licht and his colleagues report that the new approach achieves a hydrogen-production efficiency of 30 percent and has the potential to do even better. Another Licht-led team held the previous efficiency record of 18 percent using specialized solar cells (SN: 9/16/00, p. 182: Device ups hydrogen energy from sunlight).


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