Breakthrough in green hydrogen energy production found in Janus materials

Hydrogen energy is a promising option for a carbon-neutral energy source. However, nearly all hydrogen fuel is currently created with methane, meaning its production releases as much carbon dioxide as is produced using an equivalent amount of gasoline. Photocatalytic water splitting could make hydrogen fuel greener, but major efficiency limitations remain, including pH-dependent performance and low solar-to-hydrogen (STH) efficiency.

To address the shortcomings of existing photocatalysts, Li et al. designed an ultrathin two-dimensional material with an asymmetric Janus structure that creates an intrinsic electrical field through out-of-plane polarization. The Janus material, which has a structure without mirror symmetry, allowed for the optimization of water splitting across a wide range of pH levels, overcoming a major limitation of previous photocatalysts.

Additionally, stacking the material in optimized layers broke bandgap lower limits and more than doubled the STH efficiency as compared to conventional photocatalyst materials. The efficiency was maintained within one percent for a range of neutral to alkaline water pH levels, negating previous tradeoffs between efficiency and pH adaptability

“This work paves the way for industrial hydrogen production,” said author Wei-Qing Huang. “Imagine solar farms equipped with our pH-tolerant catalysts, generating hydrogen fuel even with fluctuating water quality — a potential game-changer for regions lacking infrastructure.”

The researchers are currently working to scale the material to ensure it retain its properties under real-world conditions. In addition to testing the material’s durability, the researchers are also developing a database to identify more materials that could further improve photocatalytic efficiency.

Source: “Out-of-plane polarization engineering: Optimizing exciton dissociation and solar-to-hydrogen efficiency in photocatalytic water splitting,” by Lei Li, Zi-Xuan Yang, Tao Huang, Hui Wan, Jianhang Nie, Gui-Fang Huang, Wangyu Hu, and Wei-Qing Huang, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0267520 .