Rational engineering of metal-organic coordination networks into facet-controlled phosphides for overall water splitting

Although transition metal phosphide electrocatalysts display unique electronic structure that serves as functional centers for hydrogen evolution reaction, the synthesis of this class of materials for oxygen evolution remains a challenge due to the complex multielectron transfer pathways and sluggish reaction kinetics. This study details an in-situ modification and transformation of cyanide-bridged nickel-iron (CN-NiFe) organometallic hybrid into the preferential Fe2P phase with prevailing exposed {120(sic)} faceted active centers by leveraging on the facile coordinate cleavage dynamics and compound reactivity of labile metal organic coordination frameworks. The resultant transition metal phosphide attains high electrochemical surface area, low Tafel slope, and low overpotential for the oxygen evolution reaction, while also demonstrating bifunctional electrocatalytic performance for overall water splitting. Comprehensive experimental studies and density functional theory calculations reveal that the exceptional catalytic activity originates from the transformation of framework metallic sites into preferential active sites allows an optimal adsorption of oxygen evolution reaction intermediates.