24 April 2019
Storing solar energy: Novel catalyst for water splitting
Published online 28 November 2018
A novel method for generating durable nano-catalysts for splitting water may contribute to efficient solar power storage solutions.
Photovoltaic cells are becoming ever more efficient sources for generating renewable electricity, but they must be combined with effective methods of storing the energy from our sun. One of the cleanest ways of doing this is to convert the sun’s electrical energy into chemical energy that can then be stored and released, for example through water electrolysis. This involves splitting water into its constituent parts and using the resulting oxygen and hydrogen to generate electricity when needed.
Water splitting requires carefully designed, durable catalysts. An international team of scientists, led by Mohamed Alkordi at Egypt’s Zewail City of Science and Technology, has developed a new method for generating hybrid nanoparticle/graphene catalysts based on microporous metal–organic frameworks (MOFs).
MOFs are synthetic compounds consisting of clusters of metal ions connected by organic ligands. By subjecting MOFs to extreme heat, their chemical structure can be altered to create metal-based nanoparticles for use as catalysts. The novel ‘one-pot’ approach taken by Alkordi’s team removes the need for this energy-intensive transformation, and uses the abundant, low cost material graphene as the composite base.
The researchers deposited a microporous, zirconium-based MOF onto ultrathin graphene sheets, before adding nickel ions to the composite. They then immersed the composite in alkaline solution and passed an electric current through it, triggering a chemical reaction to restructure the composite into nickel hydroxide nanoparticles deposited on the graphene base. These nanoparticles have proven to be exceptionally active catalysts for water splitting.
“This enhanced catalytic activity and durability are consequences of our optimized composition, namely the active nickel ions, the MOF host, and the electronically conductive graphene support,” says Alkordi.
Hassan, M. H. et al. A Ni-loaded, metal–organic framework–graphene composite as a precursor for in situ electrochemical deposition of a highly active and durable water oxidation nanocatalyst. Chem. Commun. http://dx.doi.org/10.1039/C8CC07120A (2018).