Insights into the Formation, Chemical Stability, and Activity of Transient Ni_yP@NiOx Core–Shell Heterostructures for the Oxygen Evolution Reaction

Ni_yP emerged as a highly active precatalyst for the alkaline oxygen evolution reaction where structural changes play a crucial role for its catalytic performance. We probed the chemical stability of Ni_yP in 1 M KOH at 80 °C and examined how exposure up to 168 h affects its structure and catalytic performance. We observed selective P-leaching and formation of Ni_yP/NiOx core–shell heterostructures, where shell thickness increases with ageing time, which is detrimental for the activity. By tuning the particle size, we demonstrate that prevention of complete catalyst oxidation is essential to preserve the outstanding electrochemical performance of Ni_yP in alkaline media.