Cobalt Phosphide Nanoparticles Synthesized by Solvothermal Phosphidization of Metal-Organic Frameworks for Electrocatalytic Oxygen Evolution

Active and stable electrocatalysts for oxygen evolution reaction (OER) are crucial in the widespread application of water electrolyzers. Cobalt phosphide nanoparticles (Co-P) with different degrees of crystallinity are synthesized via solvothermal phosphidization of Co metal-organic frameworks and P-4 using different solvents. The Co-P can be converted to active OER electrocatalysts in 1 M KOH, with the most active reaching 10 mA cm(-2) OER current densities at 270 mV overpotential. The OER intermediate adsorption energy is tuned by the electron interactions in the crystalline/amorphous heterostructured Co-P, which show the highest intrinsic OER activity. After the long-term OER in base, surface phosphides are converted to (oxy)hydroxides that are the active species towards OER.