Polar Layered Intermetallic LaCo2P2 as a Water Oxidation Electrocatalyst

We investigate LaCo₂P₂ as an electrocatalytic material for oxygen evolution reaction (OER) under alkaline and acidic conditions. This layered intermetallic material was prepared via Sn-flux high-temperature annealing. The electrocatalytic ink, prepared with the ball-milled LaCo₂P₂ catalyst at the mass loading of 0.25 mg/cm², shows OER activity at pH = 14, reaching current densities of 10, 50, and 100 mA/cm² under the overpotential of 400, 440, and 460 mV, respectively. Remarkably, the electrocatalytic performance remains constant for at least 4 days. Transmission electron microscopy reveals the formation of a catalytically active CoO_x shell around the pre-catalyst LaCo₂P₂ core during the alkaline OER. The core serves as a robust support for the in situ-formed electrocatalytic system. Similar studies under pH = 0 reveal the rapid deterioration of LaCo₂P₂, with the formation of LaPO₄ and amorphous cobalt oxide. This study shows the viability of layered intermetallics as stable OER electrocatalysts, although further developments are required to improve the electrocatalytic performance and increase the stability at lower pH values.