Improved Electrocatalyst with Outstanding Performance and Stability for Energy Conversion Processes

Tiva Sharifi, physicist at Umeå University, Sweden has embarked on a challenging project to experimentally prove that earth-abundant materials mainly based on nitrogen, carbon, and transition metal oxides can be integrated into high performance energy conversion devices, which can be used in both electrolysis and fuel cells. Tiva Sharifi defended her thesis on 31 March 2015.

Tiva Sharifi comes from Iran. She has been studying at the Department of Physics, Umeå University, since 2009. (Photo: Ingrid Söderbergh)

Alternative energy resources are in dire need as global oil reserves continue to dwindle. An attractive approach to fuel production is the production of hydrogen by splitting water to hydrogen and oxygen with the aid of sunlight.

Tiva Sharifi has based her thesis on finding solutions to the challenges of energy conversion with a key focus on producing resilient electrode materials capable of up-scaling electrochemical cells.

I have created an electrocatalyst with outstanding performance and stability for several important energy conversion processes

Tiva Sharifi

Effective electrocatalyst materials are required for electrochemical methods to function smoothly, as these methods are not spontaneous.

Generally, prior to being loaded onto a conductive material surface, electrocatalyst synthesis is performed separately. The conductive material acts as a current collector. This combination works in the same manner as an electrode (cathode or anode) in an electrochemical cell.

However in this method, up-scaling is obstructed and the entire process has to be performed within a laboratory. Moreover, the electrode created using this method is not reliable and the catalyst material tends to peel away from the conductive substrate during the electrochemical reaction.

In the method formulated, Tiva Sharifi tried to provide solutions to the aforementioned challenges while producing electrode materials which allow the electrocatalyst synthesis step and the loading onto a conductive material step to be integrated. Sharifi applied a bottom-up self-assembly method to grow the electrocatalyst material directly on the current collector surface. The current collector was a basic low-cost conductive substrate made of carbon paper. This set up is easy to handle and up-scale as well as having satisfactory conductivity.

She chose inexpensive transition metal oxides, such as iron oxide and cobalt oxide, and organic carbon materials rather than the rare and expensive noble metals such as ruthenium and platinum.

Additionally, Tiva Sharifi also tested nitrogen-doped carbon nanotubes (NCNTs) as an electrocatalyst as their properties are appealing for manufacturing organic metal-free catalysts. The result of her testing revealed that NCNTs developed directly on the current collector were very efficient electrocatalysts.

The NCNTs display strong electrocatalytic activity for certain basic energy conversion reactions e.g., oxygen reduction reaction in fuel cells. They are formed by the introduction of nitrogen in the pure hexagonal carbon structure of carbon nanotubes. Nitrogen can be monitored in the carbon structure. The nanotubes act catalytically different based on the location where the nitrogen substitutes for carbon in the structure.

Tiva Sharifi’s thesis illustrates the possibility of transferring nitrogen from non-favourable locations to catalytically active locations in already synthesised NCNTs.

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