Economical Fe-doped Ta 2 O 5 electrocatalyst toward efficient oxygen evolution: a combined experimental and first-princi
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Research Letter
Economical Fe-doped Ta2O5 electrocatalyst toward efficient oxygen evolution: a combined experimental and first-principles study Aihong Liu, School of Materials and Metallurgy, Hubei Polytechnic University, Huangshi 435003, Hubei Province, People’s Republic of China Zhe Chen, Xiangxia Wei, Wen Xiao, and Jun Ding, Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore Address all correspondence to Jun Ding at [email protected] (Received 12 January 2017; accepted 6 July 2017)
Abstract A non-precious metal catalytic system of Fe-doped Ta2O5 is developed by pulsed laser deposition toward efficient oxygen evolution reaction (OER). The optimal Fe concentration is determined to be 5 at.% for optimized OER activity via a series of electrochemical characterizations. The 5 at.% Fe-doped Ta2O5 nanolayer possesses a low onset overpotential of 0.22 V, an overpotential of 0.38 V at 10 mA/cm2 and a Tafel slope of 54 mV/dec. Comprehensive first-principles calculations attribute the enhanced OER activity to the substitutional FeTa dopants, which generate a new active OER site on surface and simultaneously accelerate electron transfer over oxygens.
Introduction To meet the challenges of energy crisis and global warming, efficient and clean utilization of renewable energy sources, especially solar energy, is a necessity.[1–4] In addition to solar cell, solar-to-fuel and solar-to-hydrogen conversion, such as photocatalytic CO2 reduction or water splitting, have recently attracted enormous interests for producing energy directly from sunlight and simultaneously storing the energy in the form of chemical fuels.[2,5] However, the overpotential induced by the anodic oxygen evolution reaction (OER) is usually much higher than that of the cathodic reaction (e.g., hydrogen evolution reaction) and limits the overall efficiency of energy conversion. It points out the prime importance of accelerating the sluggish OER.[6–11] Moreover, rapid OER also ensures the high efficiency of water electrolysis and rechargeable metal-air batteries, further emphasizing the urgency of designing high-performance OER catalysts.[12–15] IrO2 or RuO2 are conventional OER catalysts, which are unfortunately not possible for large-scale applications due to the high cost and scarcity.[16–19] As a result, searching for earth-abundant alternatives with high OER activity to replace the previous-metal catalysts forms a hot topic. Transition metal compounds, particularly oxides/hydroxides of Fe, Co, Ni, Ta, Mn, and Cu as well as their mixtures, have been reported to be highly active in OER catalysis.[12,20–22] Therein, the OER catalysts involving element Fe attract tremendous attention owing to the high activity. Burke et al. report that the composition of Fe in Co–Fe (oxy)hydroxide is critical for optimizing the OER activity.[23] Moreover, Burke et al.[20] also compare the activities of various mixed
metal (oxy)hydroxide and illustrate the high OER performance of the catalysts with Fe elements. Friebel et
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