Highly Efficient and Robust One Dimensional (1D) Transition Metal Oxide Based Nanostructured Electrocatalyst Architectures for Acid Mediated Oxygen Evolution Reaction (OER) (2018)

The huge consumption of conventional fossil fuels for meeting the energy demand has led to major unsustainable environmental concerns; warranting the identification and development of clean and non-carbonaceous energy sources 1, 2 . In this aspect, hydrogen has been well-known as a clean, non-carbonaceous and potential future energy source with superior energy density than currently adopted carbonaceous energy sources 1, 3 . However, efficient and economic production along with cost-effective storage and distribution of hydrogen utilizing clean non-carbonaceous approach is of paramount importance before universal adoption of hydrogen as a clean energy source in the impending non-carbonaceous fuel economy 2 . Along these lines, electricity driven water splitting is considered as a frontrunner for hydrogen production 4, 5 . However, commercial development of water electrolysis has witnessed major obstacles due to the need for expensive platinum group metals (PGM) based electro-catalysts (Pt, RuO 2 , IrO 2 ) which exhibit excellent electro-catalytic activity and stability for kinetically sluggish oxygen evolution reaction (OER) in acid assisted proton exchange membrane (PEM) based water electrolysis that has major advantages. Therefore, the identification and development of novel and ultra-low noble metal or noble metal free electro-catalysts exhibiting excellent electro-catalytic activity and superior long term electrochemical stability in highly acidic operating conditions of OER, will aid in the reduction of capital cost of water electrolysis cells(~$2/KgH 2 ) and thus, augmenting the progression towards successful commercialization 1 . Thus, aiming at this goal for the significant improvement in the OER kinetics and also to achieve the superior electro-catalytic activity towards OER, tailoring of the material length scale to one-dimensional (1D) architecture is one of the most promising catalyst development strategies. Over the past few years, electro-catalysts with 1D nanostructured morphologies such as nanowires (NWs), nanorods (NRs) as well as nanotubes (NTs) have garnered significant attention as potentially effective materials for water splitting due their inherent benefits 6 . Therefore, in the present study, based on our theoretical first principles calculations of the total energies and electronic structures, we have explored the generation of 1D nano structured-morphology ( Fig.1 ) of the earth abundant F substituted transition metal oxide based powder electrocatalyst system. The as-synthesized electrocatalyst system exhibits remarkably higher electro-catalytic activity and excellent stability for acidic OER. The as-synthesized 1D electrocatalyst exhibited significantly lower charge transfer resistance (R ct ) than benchmark noble metal based OER catalysts and many other precious/non-precious electrocatalysts systems . In addition, the as-synthesized 1D electrocatalyst displayed remarkable activity and approached a current density of ~ 10 mA/cm 2 at an overpotential of ~ 200 mV. In summary, we have synthesized high performance, robust 1D ultra low noble metal containing OER electrocatalyst system for PEM water splitting. The enhanced electrocatalytic activity of this electro-catalyst is majorly attributed to the modification of electronic structure and lower charge transfer resistance (i.e. lower activation polarization owing to 1D architecture). Thus, we believe that the present architecture of the electrocatalyst system is indeed promising and reliable for the cost-effective and sustainable hydrogen production. The results of this work will be presented and discussed. Acknowledgements: Financial support of NSF-CBET grant# 1511390, Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) is acknowledged. References: S. D. Ghadge, P. P. Patel, M. K. Datta, O. I. Velikokhatnyi, R. Kuruba, P. M. Shanthi and P. N. Kumta, RSC Advances , 2017, 7 , 17311-17324. P. P. Patel, O. I. Velikokhatnyi, S. D. Ghadge, P. J. Hanumantha, M. K. Datta, R. Kuruba, B. Gattu, P. M. Shanthi and P. N. Kumta, International Journal of Hydrogen Energy , 2018. S. Ghadge, M. Chavan, A. Divekar, A. Vibhandik, S. Pawar and K. Marathe, Separation Science and Technology , 2015, 50 , 365-372. P. P. Patel, O. I. Velikokhatnyi, S. D. Ghadge, P. H. Jampani, M. K. Datta, D. Hong, J. A. Poston, A. Manivannan and P. N. Kumta, International Journal of Hydrogen Energy , 2017, 42 , 24079-24089. S. D. Ghadge, P. P. Patel, M. K. Datta, O. I. Velikokhatnyi, R. Kuruba, P. M. Shanthi and P. N. Kumta, RSC Advances , 2017, 7 , 17311-17324. J. Li and G. Zheng, Advanced Science , 2017, 4 . Figure 1