Efficient Dual-Site Carbon Monoxide Electro-Catalysts Via Interfacial Nano-Engineering

Abstract

Durable, highly efficient, and economic sound electrocatalysts for CO electrooxidation (COE) are the emerging key for wide variety of energy solutions, especially fuel cells and rechargeable metal−air batteries. Herein, we report the novel system of nickel−aluminum double layered hydroxide (NiAl-LDH) nanoplates on carbon nanotubes (CNTs) network. The formulation of such complexes system was to be induced through the assistance of gold nanoparticles in order to form dual-metal active sites so as to create a extended Au/NiO two phase zone. Bis (trifluoromethylsulfonyl)imide (NTf 2 ) anion of ionic liquid electrolyte was selected to enhance the CO/O 2 adsorption and to facilitate electrocatalyzed oxidation of Ni (OH) 2 to NiOOH by increasing the electrophilicity of catalytic interface. The resulting neutral catalytic system exhibited ultra-high electrocatalytic activity and stability for CO electrooxidation than commercial and other reported precious metal catalysts. The turnover frequency (TOF) of the LDH-Au/CNTs COE catalyst was much higher than the previous reported other similar electrocatalysts, even close to the activity of solid-gas chemical catalysts at high temperature. Moreover, in the long-term durability testing, the negligible variation of current density remains exsisting after 1000 electrochemistry cycles.Advanced electrocatalysts can power sustainable and efficient fuel cells, metal-air batteries, and electrolyzers. Major advances have been made arising from the emerging field of "surface electrocatalysis" in terms of not only electrocatalysis, but also energy conversion. Low-temperature CO electrooxidation (COE) is one of the most significant processes that critical for the large scale production and storage of natural gas in the chemical form. However, CO catalytic oxidation proceeds at the gas-solid interface through a multi-step kinetically sluggish electron transfer, which may result in deteriorating CO electrocatalysis, and so forth. Effective and sustainable electrocatalysts can reduce the over-potential, expedite the reaction, and maintain the stability, all of which can largely boost the energy conversion efficiency. Traditional Pt/Ru-based alloys in acidic solution have been used as alternatives to more active and CO tolerant electrocatalysts 1 . However, the CO tolerance and activity is still insufficient for commercialization.The heterogeneous catalysts with enhanced activities at high temperatures have been recently studied due to the development of multicomponent active sites, particularly Au-metal hydroxide and oxide interfaces. In this condition, dual-metal catalytic sites with Au adjacent to oxide have shown higher catalytic activity for CO oxidation via two pathways, (1) increasing the perimeter of the boundary area for gas adsorption, and (2) forming higher activity metal complex with designed metal/ligands combination 2-6 . However, most high activity catalysis systems are in solid/gas-phase chemical system at high temperatures. Promoted electrocatalyst/electrolyte system at room ...