CoFe alloy realizing enhanced Fe-bridged electron superhighways in Mott-Schottky heterojunctions for efficient water and urea electrolysis

Abstract

As a typical Mott-Schottky, the conventional single-metal/semiconductor junctions suffer from limited electronic modulation capability and reaction adaptability. This work developed a controllable synthesis strategy based on the Mott-Schottky theory and Prussian blue analog precursors, successfully constructing a CoFe/Co₂P heterostructure by integrating bimetallic nanoalloys with phosphide semiconductors. Experimental characterization and theoretical calculations confirmed the continuous electron enrichment at the Co site. The low electronegativity of Fe, as the electron donor, expanded the interfacial work function difference (ΔΦ), and synergistically optimized the d-band electronic structure and intermediate adsorption by accelerating charge transfer kinetics. Consequently, the CoFe/Co₂P heterostructure exhibits superior multi-reaction activity compared to pure Co₂P and Co/Co₂P in the urea oxidation reaction, oxygen evolution reaction (OER), and hydrogen evolution reaction in alkaline media. In situ characterization further demonstrated that the urea molecule was directly oxidized at the CoFe/Co₂P interface site, avoiding the formation of the rate-limiting step CoOOH in the OER, which has rarely been mentioned in previous studies, thereby achieving faster kinetics at a significantly reduced potential. Accordingly, the assembled two-electrode urea oxidation-assisted hydrogen production electrolytic cell only requires 1.314 V to drive a current density of 10 mA cm⁻², which is lower than the overall water splitting (1.691 V). This research provides a new interface control strategy for the rational design of efficient hydrogen production catalysts.