A team of Scottish-based scientists are developing a new system to produce hydrogen (H2) from solar energy.

The high cost and low efficiency of producing H2 from sunlight is being tackled by scientists at Heriot-Watt University in Edinburgh.

Dr Jin Xuan (below), Assistant Professor of Mechanical Engineering, and the Associate Director of Research Centre for Carbon Solutions at Heriot-Watt University, and colleagues from Yale, the City University of Hong Kong and the East China University of Science and Technology are developing a new system to produce H2 from solar energy using a technique known as photoelectrochemical (PEC) water splitting. The technique uses solar energy to split the H2 and oxygen (O2) in water and collect the H2 as a renewable energy source.

Hwu 011 jin xuan

Source: Heriot-Watt University

A press release explained, “Until now, a minimum supply of 1.23 electron volts (eV) was required to split the water, and only small part of sunlight, the UV range, could be used, meaning the rest of the spectrum’s energy was wasted.”

Xuan’s team has lowered the energy requirements of PEC water splitting to 0.35 eV, by developing a pH-differential design. By changing the pH of each electrode individually, the scientists change the whole thermodynamics of the process, meaning a wider spectrum of sunlight and much cheaper materials can be used.

The innovative microsystem generates unique microfluidic patterns to accommodate the pH differential, and acid and alkaline electrolytes can coexist in a single cell.

The new system will reduce the cost of PEC water splitting by around two thirds and increase the solar to fuel efficiency by up to 20%.

Hwu 009 jin xuan

Source: Heriot-Watt University

Xuan said: “This project offers the chance to make PEC water splitting a viable route for H2 production.”

“The main barrier to solar H2 production in the UK, and globally, is its high cost - it costs twice as much to produce as energy from wind and biomass.”

“Our system will use cheap, widely available materials that mean the technology can be easily scaled up to meet the growing demand for H2 fuel.”

“We have already proved that this system has potential. We’ve applied a similar design strategy in a number of energy devices, such as fuel cells and batteries.”

Xuan’s project was funded by the Engineering and Physical Sciences Research Council, and is conducted in partnership with Yale’s Energy Sciences Institute, the City University of Hong Kong and East China University of Science and Technology.