New material can extract energy and clean water from wastewater

In a world in which fresh water become a scarce good and where there is never sufficient energy, any material that can help produce either is very much valued. Imagine how great a material that can do both would be. This dream has become a reality, thanks to researchers at the King Abdullah University of Science and Technology (KAUST), who have created a material that can produce clean water and hydrogen from wastewater.

The researchers made a tube from a non-conductive polymer and coated it with a thin layer of platinum to create a filtration membrane. The tubular shape has as an advantage that it has a better surface area to volume ratio than porous, flat electrodes have, which previously have been used as a filter.

These electrochemical membrane bioreactors they created recover clean water for reuse and energy from wastewater by integrating micro- or ultrafiltration membrane cathodes with a microbial electrochemical system. This works by using a material full of pores small enough to block the passage of bacteria while allowing treated, clean water to pass through. The same material also acts as an electrode in an electrochemical circuit that recovers energy through the hydrogen-evolution reaction.

Materials made from polymers are cheap to produce and flexible, but because they act as electric insulators, they are not often used as electrodes. To address this problem, the researchers coated the polymer with a layer of platinum, allowing the material to act as a catalyst for the hydrogen evolution reaction, in which hydrogen is produced through the process of water electrosis.

Despite significantly lower platinum loading, the researchers confirmed that the hydrogen-evolution reaction of their material was similar to that of a platinum-carbon cloth, a material combination typically used for this application.

The fibres can potentially be applied to directly convert carbon-dioxide waste from industrial sources to value-added products, such as methane and acetate, through microbial electrosynthesis.

Diagram: KAUST