A series of CuCo 2 O 4 catalysts were synthesized by pore forming, sol-gel, spray pyrolysis and sacrificial support methods. Catalysts were characterized by XRD, SEM, XPS and BET techniques. The electrochemical activity for the oxygen reduction and oxygen evolution reactions (ORR and OER) was evaluated in alkaline media by RRDE. Density Functional Theory was used to identify two different types of active sites responsible for ORR/OER activity of CuCo 2 O 4 and it was found that CuCo 2 O 4 can activate the O-O bond by binding molecular oxygen in bridging positions between Co or Co and Cu atoms. It was found that the sacrificial support method (SSM) catalyst has the highest performance in both ORR and OER and has the highest content of phase-pure CuCo 2 O 4 . It was shown that the presence of CuO significantly decreases the activity in oxygen reduction and oxygen evolution reactions. The half-wave potential (E 1/2 ) of CuCo 2 O 4 -SSM was found as 0.8 V, making this material a state-of-the-art, unsupported oxide catalyst. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0921504jes] All rights reserved.Manuscript submitted December 3, 2014; revised manuscript received January 28, 2015. Published February 7, 2015 Development of highly active bi-functional catalysts, in reactions of oxygen reduction/oxygen evolution (ORR/OER), attracts the attention of not only researchers in academia, but also from industrial R&D centers. The industrial interest is apparent by the growing market for supplying pure hydrogen and oxygen for fuel cell back-up power systems in India and Africa. Presently, both fuel cells and electrolyzers utilize a substantial amount of platinum-group metals (PGM), mainly platinum for ORR and IrO 2 for OER. Despite the fact that platinum is the most active catalyst for oxygen reduction, it has a high price; the discovered resources are scarce and major mining facilities are located in politically unstable countries. On the other side, iridium is one of the least abundant elements in the Earth's crust, making its application commercially unviable. The combination of these factors leads to the problem of the incredibly high price of fuel cell stacks and electrolyzers. There is substantial progress in substituting platinum from the cathode side of fuel cell MEAs, 1 while there has been no such breakthrough for electrolyzers reported in open literature.Secondly, there is a promising application for bi-functional catalysts in metal-air batteries, especially Lithium-air batteries. Li-air batteries should effectively reduce oxygen during the discharge cycle and evolve oxygen during the charge cycle. Highly efficient catalysts for those cycles are precious metal-based materials: Pt, Au, Ag, Pd. 2,3Li-air batteries and electrolyzers will be bro...

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To achieve a better understanding of the CO2 reduction reaction on carbon-based electrocatalysts, we synthesized a library of nitrogen-doped carbonaceous materials with atomically dispersed 3d transition metals and corresponding metal-free electrocatalysts. The sacrificial support method was used yielding catalyst materials of high dispersity and high graphitic content. The resulting electrocatalysts were impurity free, hence allowing a better understanding of the mechanism of CO2 reduction. By combining the electrochemical results with density functional theory, we were able to separate the electrocatalysts into several categories, based on their CO2 → COOHads free energy and their COads binding strength. The “strong-CO binder” electrocatalysts (e.g., Cr, Mn and Fe–N–C) achieved a Faradaic efficiency up to 50% at −0.35 V vs. RHE (at pH = 7.5, in 0.1 M phosphate buffer). Such Faradaic efficiency was also achieved for a metal-free electrocatalyst, therefore showing the high activity of the metal-free, N-containing, moieties toward the CO2 reduction reaction. This was confirmed by near ambient pressure X-ray photoelectron spectroscopy that confirmed pyridinic and hydrogenated (pyrrolic) nitrogen moieties act as preferential adsorption sites for the CO2 on the Fe–N–C catalyst surface.

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Conversion of biomass-derived molecules involves catalytic reactions under harsh conditions in the liquid phase (e.g., temperatures of 250 °C and possibly under either acidic or basic conditions). Conventional oxide-supported catalysts undergo pore structure collapse and surface area reduction leading to deactivation under these conditions. Here we demonstrate an approach to deposit graphitic carbon to protect the oxide surface. The heterogeneous catalysts supported on the graphitic carbon/oxide composite exhibit excellent stability (even under acidic conditions) for biomass conversion reactions.