Researchers from the Daegu Gyeongbuk Institute of Science and Technology (DGIST) and Kookmin University have developed a photocatalyst for producing hydrogen from water using sunlight. The work was published in the journal Small. The project was led by Professor Jongmin Choi and Professor Yonghun Kim, and the first authors of the article were Dr. Jin Young Park and graduate student Haejeong Kim.
Typically, such devices use titanium dioxide (TiO2) - it is stable but absorbs only ultraviolet light, which limits efficiency. To broaden the absorption spectrum, scientists add nanomaterials based on silver and bismuth. However, the traditional deposition method requires a voltage above 200 volts and toxic organic solvents, which contradicts the idea of environmentally clean hydrogen production.
The Korean researchers replaced the molecules on the surface of the nanocrystals with hydrophilic ones - those that interact well with water - and applied the method of "aqueous electrophoretic deposition." In it, particles are deposited onto an electrode under low voltage in an aqueous solution. As a result, the voltage was reduced from 200 to 4 volts - roughly that of an ordinary battery. The coating is applied in three minutes in a safe aqueous solution without toxic solvents, which eliminates surface damage and the formation of impurities that occurred at high voltage.
The new photocatalyst under illumination showed a photocurrent (the current generated under the action of light) about ten times higher than that of conventional electrodes made of a single material. Under conditions close to natural sunlight, the photocurrent density reached 3.0 mA/cm2. After two hours of continuous illumination, the electrode retained 65.1% of its initial performance, and gas analysis confirmed the release of hydrogen.
The authors note that the development contains no lead or cadmium and requires significantly less organic solvents and high voltage, which could accelerate the commercialization of environmentally clean "green" hydrogen. "The significance of the work is that we achieved high efficiency of hydrogen production using a safe and clean aqueous low-voltage process, overcoming the limitations of traditional methods," DGIST's press service quoted Choi as saying. In his opinion, this will become an important basis for accelerating the practical application of eco-friendly hydrogen production technologies.