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 CoOx 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.