New High Performance Photocatalyst and Hybrid Photocatalytic-Electrolysis System Could Significantly Reduce Voltage Required and Cost for Hydrogen Production

Top: Mechanism of the photocatalytic-electrolysis system. Bottom: New high-performance photocatalyst (inset) and overall model of the system. Source: AIST. Click to enlarge.

Researchers at Japan’s National Institute of Advanced Industrial Science and Technology (AIST) have developed a tungsten oxide (WO₃) photocatalyst that provides a significantly higher quantum yield under visible light than conventional photocatalysts.

The new catalyst is applied in a hybrid photocatalytic-electrolysis system that uses the photocatalytic reaction converting solar energy to lower the electrolysis voltage required for the hydrogen production by water electrolysis. AIST researchers say that the use of solar energy can reduce the voltage required for water electrolysis by almost 50%, leading to lower-cost production of hydrogen.

Potential diagram of various reaction mechanisms for hydrogen production via water decomposition. (a) Water decomposition by photocatalyst. (b) AIST’s newly developed photocatalyst-electrolysis hybrid system. (c) Ordinary water electrolysis: high voltage is required. Source: AIST. Click to enlarge.

The photocatalyst generates oxygen by oxidizing water and reducing iron(III) ions (Fe³⁺) to iron(II) ions (Fe²⁺). The system also involves low-voltage electrolysis in which water is reduced to generate hydrogen and Fe²⁺ ions are oxidized to Fe³⁺ ions.

The high efficiency of the WO₃ photocatalyst was achieved using a new method—treatment of the surface of the photocatalyst with Cesium (Cs)