Consumed by thirst, miles from home, the hiker must decide whether to drink and risk 

infection from whatever bacteria are in the puddle, or endure dehydration. But that hik

er might one day be able to drink worry free, thanks to a new kind of water purifier tha

t uses sunlight and water to produce hydrogen peroxide, a powerful and common antis

eptic.

The experimental water purifier, developed in the lab of Xiaolin Zheng, associate profes

sor of mechanical engineering, is a variant of the better-known process of using solar e

nergy to split water into hydrogen, a clean-burning fuel, and oxygen, a life-sustaining e

lement. But, as the team describes in the journal Advanced Energy Materials, instead 

of fully splitting oxygen and hydrogen, the new process reduces oxygen and oxidizes 

water to produce hydrogen peroxide, or H2O2.

Even just a small amount will purify the water, she says. Hydrogen peroxide disinfects 

water at a level of tens of parts per million. That's about two tablespoons in 25 gallons 

of water. In tests using tap water, the Stanford system easily reached well over 400 par

ts per million of H2O2 in five hours.

Zheng says the team will have to change some of the materials in the process to make its 

blend of ordinary water and hydrogen peroxide safe to drink. But they think that one day, a 

person in desperate thirst could pull out their lightweight solar purifier, pour in some suspect 

H2O and, given enough time, produce enough H2O2 through the sun-activated process to

turn any fresh water into a veritable oasis.

In addition to future drinking water applications, Zheng and Xinjian Shi, the graduate student 

leading the project, also imagine that their system might be adapted into self-sustaining 

swimming pools purified with solar-created hydrogen peroxide rather than chlorine, or solar-

powered water purification stations for use in developing regions where fresh water is a 

precious commodity.