Abstract
Development of earth-abundant electrocatalysts for hydrogen evolution and oxidation reactions in strong acids represents a great challenge for developing high efficiency, durable, and cost effective electrolyzers and fuel cells. We report herein that hafnium oxyhydroxide with incorporated nitrogen by treatment using an atmospheric nitrogen plasma demonstrates high catalytic activity and stability for both hydrogen evolution and oxidation reactions in strong acidic media using earth-abundant materials. The observed properties are especially important for unitized regenerative fuel cells using polymer electrolyte membranes. Our results indicate that nitrogen-modified hafnium oxyhydroxide could be a true alternative for platinum as an active and stable electrocatalyst, and furthermore that nitrogen plasma treatment may be useful in activating other non-conductive materials to form new active electrocatalysts.
Highlights
Development of earth-abundant electrocatalysts for hydrogen evolution and oxidation reactions in strong acids represents a great challenge for developing high efficiency, durable, and cost effective electrolyzers and fuel cells
Gold foil was chosen as a substrate because it is stable over a large potential range without showing measureable hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) activity during the electrochemical polarization experiments, and roughened Au improved the physical stability of the HfOxthin films during H2 generation and enabled improved characterization using surface enhanced Raman spectroscopy (SERS)
The Hf film was oxidized by air exposure and exposed to a N2 plasma in a dielectric barrier discharge (DBD) reactor (Supplementary Figure 1) to incorporate nitrogen to form a hafnium oxynitride (HfNxOy) material
Summary
Development of earth-abundant electrocatalysts for hydrogen evolution and oxidation reactions in strong acids represents a great challenge for developing high efficiency, durable, and cost effective electrolyzers and fuel cells. We report that hafnium oxyhydroxide with incorporated nitrogen by treatment using an atmospheric nitrogen plasma demonstrates high catalytic activity and stability for both hydrogen evolution and oxidation reactions in strong acidic media using earth-abundant materials. The search for cost-effective, earth-abundant electrocatalytic materials for PEM electrolysis with high activity and stability has identified several classes of inorganic materials that are highly active for hydrogen evolution in acidic media[12,13,14]. Transition metal carbides such as WC and Mo2C are promising nonprecious metal alternatives to Pt for HER15. This material demonstrates the excellent HOR and HER activities in acids using nonPGM catalysts, opening new opportunities to develop technologically and economically viable unitized regenerative fuel cell (URFC) systems and cost-effective PEM electrolyzers
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