Nickel and Nitrogen-Doped Bifunctional ORR and HER Electrocatalysts Derived from CO<sub>2</sub>
Anna-Liis Remmel, Sander Ratso, Giorgio Divitini, Mati Danilson, Valdek Mikli, Mai Uibu, Jaan Aruväli, Ivar Kruusenberg
Abstract
While nonprecious metal catalysts (NPMCs) have been shown to be viable alternatives for Pt-based catalyst materials in both proton exchange membrane fuel cells (PEMFCs) and electrolyzers, all of the synthesis methods of these materials still have a positive carbon footprint. This means that, while the production of CO2 is avoided by converting to a hydrogen economy, a large amount of CO2 must be produced to drive this transition (as much as 600 kg of CO2 per kilogram of catalyst for CVD-based materials). Here, we demonstrate, for the first time, a sustainable method for synthesizing a bifunctional oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) catalyst directly from CO2 in a process that captures carbon dioxide from the atmosphere or flue gases instead of producing it as all previous methods for creating ORR/HER catalysts. The electocatalytic activity of the material is correlated to its structure and synthesis conditions by a thorough physicochemical analysis including rotating disk electrode (RDE) measurements, porosity analysis with N2 physisorption, scanning and transition electron microscopy imaging (SEM, TEM) and X-ray analysis of the materials’ crystal structure and elemental composition. The material shows promising activity and paves way for a dual approach on reducing the CO2 footprint of the energy economy.