Targeted Synthesis of Metal Dual Atom Electrocatalysts

Abstract

Natural enzymes present within their structure active centres composed of earth-abundant metals in atomic proximity. Such active sites, dual atom catalysts, display a unique efficiency in catalytic processes such as the nitrogen conversion to ammonia, the production of ethylene through C-C coupling, or the oxygen reduction reaction in fuel cells amongst others.1,2 Theoretical calculations suggest that the high catalytic activity of dual atom catalysts arises from the different binding mode of reactant molecules to that of metal foils and single atom catalysts, which allows to break transition scaling relationships.3 Nevertheless, the experimental synthesis and characterisation of this class of materials is highly challenging.4 It is particularly difficult to avoid the formation of single atom catalysts or nanoparticles. In this work we show a general approach to fabricate bioinspired Fe dual atom catalysts in a nitrogen doped carbon support; we test the catalyst for the oxygen reduction reaction under acidic conditions. The catalyst exhibited an activity of 2.4 ± 0.3 A g-1 carbon at 0.8 V versus a reversible hydrogen electrode in acidic media, comparable to the most active in the literature. The two-step procedure leads to well defined Fe-based dimers. We characterised these materials by means of X-ray absorption spectroscopy (XAS) and scanning transmission electron microscopy. Our general approach providing a new towards targeted synthesis of dual atom electrocatalysts for energy-critical reactions.References(1) Chen, J. G.; Crooks, R. M.; Seefeldt, L. C.; Bren, K. L.; Bullock, R. M.; Darensbourg, M. Y.; Holland, P. L.; Hoffman, B.; Janik, M. J.; Jones, A. K.; Kanatzidis, M. G.; King, P.; Lancaster, K. M.; Lymar, S. V; Pfromm, P.; Schneider, W. F.; Schrock, R. R. Beyond Fossil Fuel–Driven Nitrogen Transformations. Science 2018, 360, eaar6611(2) Lee, C. C.; Hu, Y.; Ribbe, M. W. Vanadium Nitrogenase Reduces CO. Science 2010, 329, 642(3) Singh, A. R.; Montoya, J. H.; Rohr, B. A.; Tsai, C.; Vojvodic, A.; Nørskov, J. K. Computational Design of Active Site Structures with Improved Transition-State Scaling for Ammonia Synthesis. ACS Catal. 2018, 8, 4017–4024(4) Pedersen, A.; Barrio, J.; Li, A.; Jervis, R.; Brett, D. J. L.; Titirici, M. M.; Stephens, I. E. L. Dual-Metal Atom Electrocatalysts: Theory, Synthesis, Characterization, and Applications. Adv. Energy Mater. 2021, 2102715 Figure 1