A new device shows promise in purifying polluted air, while at the same time producing hydrogen, which can be stored for use as a clean energy source.

A team of researchers from two Belgian schools, the University of Antwerp and KU Leuven, have discovered a process that can be used to address two disparate yet related issues – the need for air pollution mitigation and cleaner energy sources – with nanomaterials and sunlight.

Air pollution is one of the big silent killers in the modern world, and although we’re seeing progress toward cleaner energy sources and cleaner fuels and engines, which bodes well for the long-term future, we still need solutions for cleaning existing pollutants out of the air. There’s no shortage of ideas and beta projects for decreasing air pollution, including giant vacuums that harvest pollution to be turned into jewelry, tailpipe devices that capture soot in order to turn it into ink, bicycles that eat air pollution, and smog-reducing billboards, but the new development out of Belgium could become an air purifying two-fer.

According to the team that developed the process, the nanomaterials used as a catalyst in the device’s membrane are essentially the same as those used previously to extract hydrogen from water. However, the research lead, Professor Sammy Verbruggen, says that it’s not only possible to use the same type of materials to produce hydrogen from polluted air, but it’s also "even more efficient." The team’s device is a rather small-scale prototype, only a few square centimeters in size, but with some additional improvements could eventually be scaled up "to make the process industrially applicable."

"We used a small device with two rooms separated by a membrane. Air is purified on one side, while on the other side, hydrogen gas is produced from a part of the degradation products. This hydrogen gas can be stored and used later as fuel, as is already being done in some hydrogen buses, for example." – Professor Sammy Verbruggen (UAntwerp/KU Leuven)

The process uses sunlight as the energy input for the device, which is described as an "all-gas-phase unbiased photoelectrochemical cell" which converts volatile organic pollutants into CO2 at one photoanode, while also harvesting hydrogen gas at the cathode.

"Without applying any external bias, organic contaminants are degraded and hydrogen gas is produced in separate electrode compartments. The system works most efficiently with organic pollutants in inert carrier gas. In the presence of oxygen, the cell performs less efficiently but still significant photocurrents are generated, showing the cell can be run on organic contaminated air." – ChemSusChem 7/2017

It might be quite some time before the process and materials are sufficiently optimized to be put into use on an industrial scale, but the researchers’ progress speaks to a future where air pollution becomes a potential energy source instead of an energy sink and major health concern. The full paper, for those in the know, is available in the journal ChemSusChem under the title "Harvesting Hydrogen Gas from Air Pollutants with an Unbiased Gas Phase Photoelectrochemical Cell."