Hydrogen Generation from Water for Sustainable Energy Production

A new approach for water splitting using functionalized graphene oxide

Due to the development of modern society and an increasing population in the world, energy consumption is growing dramatically. However, the reserves of fossil fuels on Earth are limited; therefore, the development of sustainable energy sources has become an urgent need for the future of humanity. One of the most promising sustainable energy sources is hydrogen, which is a zero-emission fuel when burned with oxygen. It can be used in electrochemical cells or internal combustion engines to power vehicles or electrical devices. Photocatalytic reactions, which are initiated by light energy, are considered to be the most effective method for hydrogen generation.

Recently, Dr. Josep Puigmartí-Luis et al. have reported a new straightforward method to generate materials that have great potential for water splitting applications. In this method, the authors used graphene oxide, a two-dimensional material consisting of a single layer of carbon atoms arranged in a honeycomb structure bonded to oxygen-containing chemical groups, as the material for photocatalysis. The graphene oxide surface was doped with nitrogen-employing ionic liquids-low temperature molten salts-as the nitrogen source. Since the ionic liquid cations possess large electron affinities, they are prone to establish ion-exchange interactions with negatively charged graphene oxide sheets. Accordingly, it can be assumed that nitrogen-rich ionic liquids absorb onto the surface of the graphene oxide flakes. With the help of laser irradiation, the ionic liquids can react with the graphene oxide flakes yielding nitrogen-doped and reduced graphene oxide flakes. The replacement of functional oxygen groups on the graphene oxide sheet edge with nitrogen groups increases the water splitting activity of the material due to the interaction of graphitic nitrogen atoms with H+ions. This yields a superior photocatalytic efficiency for hydrogen evolution due to enhanced photogenerated charge separation and easier reduction of H+. Furthermore, the authors efficiently used ionic liquids simultaneously as solvents and reagents for the functionalization of graphene oxide.

This work provides an effective, fast and simple route to obtain nitrogen doped graphene oxide powder. To promote the industrialization process of hydrogen generation, they point out that future work will aim to increase the photocatalytic efficiency.

Written by Shangkun Li.

Read the full paper here.

A schematic illustration showing the interaction of graphene oxide with ionic liquids and the chemical structure of the obtained ionic-liquid doped graphene oxide


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