Nano-engineered electrocatalyst for nitrogen reduction reaction Ka Wai Hui 1 , Drew Evans 1 , Marta Llusca Jane 1 , Melanie MacGregor 2 1 University of South Australia, Australia, 2 Flinders University, Australia
Schematic of nanoengineered catalyst fabrication and untreated and nanoengineered catalyst illustrating change in mass transport and reactions. The electro-nitrogen reduction reaction (eNRR) is a promising method to store renewable energy by converting nitrogen gas into ammonia using electricity. However, ammonia produced with the current eNRR technologies is far from practical use due to low Faradaic efficiency (FE) and yield in water-based eNRR. Two major reasons for this are the competing hydrogen evolution reaction (HER) and the low nitrogen solubility 1 . Literature independently showed materials near the top of the Sabatier volcano plot 2 , nano-engineering 3 , and hydrophobicity modifications 4 would favour the eNRR and suppress the HER. However, the synergism between these three factors has not been studied yet. This work is focused on the theory and method of preparing a catalyst on a nano-structured Ti plate. A simple two-step electrochemical etching is used to create a template-free binary nanoporous structure on titanium surface. The number of pores and their sizes can be controlled independently. Metallic Ru and Mo are chosen as the catalysts. They are directly deposited onto the binary nanoporous structure by magnetron sputtering, resulting in a binder-free nano-sized catalyst on a current collector. A Nafion-like top-coat is deposited via plasma polymerization. This coating prevents direct contact of water molecules with the catalyst while allowing protons to pass through. It is also expected to create a triple-phase boundary close to the catalyst surface, allowing nitrogen bubbles to retain and shortening the diffusion distance. We expect this nano-engineered catalyst to improve FE and yield in water-based eNRR. References 1. B. H. R. Suryanto, H.-L. Du, D. Wang, J. Chen, A. N. Simonov and D. R. MacFarlane, Nat Catal , 2019, 2 , 290-296. 2. E. Skulason, T. Bligaard, S. Gudmundsdottir, F. Studt, J. Rossmeisl, F. Abild-Pedersen, T. Vegge, H. Jonsson and J. K. Norskov, Phys Chem Chem Phys , 2012, 14 , 1235-1245. 3. Z. Wang, Y. Li, H. Yu, Y. Xu, H. Xue, X. Li, H. Wang and L. Wang, ChemSusChem , 2018, 11 , 3480-3485. 4. J. Zheng, Y. Lyu, M. Qiao, R. Wang, Y. Zhou, H. Li, C. Chen, Y. Li, H. Zhou, S. P. Jiang and S. Wang, Chem , 2019, 5 , 617-633.
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