For environmentally friendly green hydrogen production, electrolysis of water is the most effective method. Catalysts are used for this purpose, and precious‑metal catalysts such as platinum, which have high hydrogen production efficiency, are employed as electrodes. However, precious‑metal catalysts are expensive to produce and their hydrogen generation efficiency decreases over time.

To address these drawbacks of precious‑metal catalysts, Professor Yongho Ra's research team at Jeonbuk National University (JBNU) (Division of Advanced Materials Engineering, Major in Information Materials Engineering) announced on the 16th that they succeeded in developing a novel composite‑nanostructure‑based nitride semiconductor photoelectrode by fabricating an electrochemically very stable nitride semiconductor with excellent solar‑to‑hydrogen conversion efficiency into a unique nanostructure. Based on much higher reliability compared with conventional precious‑metal catalysts, this technology is expected to dramatically improve hydrogen energy production efficiency.

Professor Ra and Research Professor Daeyoung Eom identified the breakthrough in "nitride semiconductors" and "high‑quality composite nanostructures." The technology proposed by the team is drawing attention worldwide because it can significantly enhance hydrogen generation efficiency via photoelectrochemical water splitting using only nitride semiconductors, without external precious‑metal catalysts, and can operate very stably over extended periods.

The research findings were published in the latest issue of Chemical Engineering Journal (IF=15.1, top 3.5%) under the title "External catalyst-free InGaN photoelectrode for highly efficient energy conversion and H2 generation."

Among semiconductor materials for photoelectrochemical water splitting, group‑III nitrides ((InxAl1-x)yGa1-yN) can encompass the water‑splitting photoelectrochemical oxidation–reduction potentials across the visible to infrared wavelength range of the solar spectrum. They are wide‑bandgap semiconductors with very high electrochemical stability, high thermal stability, long lifetimes, and broad optical absorption (UV to IR), and are attracting attention as next‑generation materials for photoelectrodes for water splitting.

Despite these advantages, high‑indium‑composition nitride (InGaN) semiconductors with broad spectral absorption have faced challenges for the fabrication and commercialization of high‑efficiency hydrogen evolution reaction (HER) photoelectrodes, due to high crystal defect densities and limited active light‑absorption regions within the material.

To overcome these issues, the team newly developed a novel composite nanostructure via metal‑organic chemical vapor deposition (MOCVD). They synthesized high‑quality, high‑indium‑composition InGaN 0D pyramid‑shaped nanostructures on the coaxial surface of GaN 1D nanowire structures, which maximize the specific surface area for light‑driven reactions, thereby maximizing solar spectrum absorption efficiency.

Furthermore, by effectively suppressing surface recombination of photogenerated charge carriers within the high‑indium InGaN nanostructures through a uniquely designed variable energy band structure, the team established for the first time a novel energy bandgap mechanism defining a quantum‑sliding transport effect that maximizes hydrogen evolution reaction efficiency.

Experimental results confirmed that the developed nitride‑semiconductor‑based composite nanostructure photoelectrode exhibited dramatically improved hydrogen generation efficiency compared with widely used precious‑metal photoelectrodes, owing to its large specific surface area and efficient charge‑carrier transport. The device also showed a marked improvement in long‑term stability, a critical drawback of photoelectrochemical water‑splitting hydrogen production, demonstrating encouraging results toward practical application.

The research team stated, "Because this core technology is manufactured by MOCVD and is scalable for mass production, it will serve as a leading enabling technology to accelerate the practical realization of green hydrogen production. Furthermore, it is expected to make a significant contribution to accelerating the green hydrogen industry in the Saemangeum region and South Korea's hydrogen economy."

Meanwhile, the core technology development was experimentally led by Research Professor Daeyoung Eom as first author on Professor Ra's team, and the work was conducted with support from the Nano and Materials Technology Development Program of the National Research Foundation of Korea.