Isolating the Electrocatalytic Activity of a Confined NiFe Motif within Zirconium Phosphate

Sanchez, J, Stevens, MB, Young, AR, Gallo, A, Zhao, M, Liu, Y, Ramos-Garcés, MV, Ben-Naim, M, Colón, JL, Sinclair, R, King, LA, Bajdich, M and Jaramillo, TF (2021) Isolating the Electrocatalytic Activity of a Confined NiFe Motif within Zirconium Phosphate. Advanced Energy Materials, 11 (20). p. 2003545. ISSN 1614-6832

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Abstract

Unique classes of active-site motifs are needed for improved electrocatalysis. Herein, the activity of a new catalyst motif is engineered and isolated for the oxygen evolution reaction (OER) created by nickel–iron transition metal electrocatalysts confined within a layered zirconium phosphate matrix. It is found that with optimal intercalation, confined NiFe catalysts have an order of magnitude improved mass activity compared to more conventional surface-adsorbed systems in 0.1 m KOH. Interestingly, the confined environments within the layered structure also stabilize Fe-rich compositions (90%) with exceptional mass activity compared to known Fe-rich OER catalysts. Through controls and by grafting inert molecules to the outer surface, it is evidenced that the intercalated Ni/Fe species stay within the interlayer during catalysis and serve as the active site. After determining a possible structure (wycherproofite), density functional theory is shown to correlate with the observed experimental compositional trends. It is further demonstrated that the improved activity of this motif is correlated to the Fe and water content/composition within the confined space. This work highlights the catalytic enhancement possibilities available through zirconium phosphate and isolates the activity from the intercalated species versus surface/edge ones, thus opening new avenues to develop and understand catalysts within unique nanoscale chemical environments.