Phosphorous vacancy rich Fe doped Ni₂P embedded in N, P dual doped carbon as a highly efficient electrocatalyst for the oxygen evolution reaction

초록

The growing threats of global warming and energy crises have intensified the demand for renewable energy storage and conversion technologies. Hydrogen, with its high energy density per unit mass and ease of storage and transport, has emerged as a promising alternative to fossil fuels. Among hydrogen production methods, steam reforming operates under harsh conditions, while water electrolysis generates high-purity hydrogen under mild conditions without producing pollutants. Electrochemical water splitting involves two key reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. While HER is a relatively simple two-electron transfer process, OER is a more complex four-electron transfer reaction characterized by high overpotential and slow kinetics. Consequently, the development of efficient and durable OER catalysts is critical for advancing commercial water electrolysis. Although noble metal-based catalysts are widely used for OER, their high cost and limited stability present significant challenges, necessitating the development of cost-effective alternatives. Transition metal-based materials, including nitrides (TMNs), oxides (TMOs), and phosphides (TMPs), have been proposed as promising substitutes. Among these, TMP have garnered considerable attention due to their abundance; however, their practical application is constrained by low conductivity and insufficient active sites. Strategies such as metal doping to modulate surface electronic structures and adsorption energies, as well as introducing surface defects to increase active site density, have shown potential for enhancing OER performance. In this study, Fe-doped Ni₂P nanoparticles with abundant phosphorus vacancies were synthesized through a series of processes, including precipitation, polymerization, phosphorization, and partial reduction. Initially, NiFe Prussian blue analogs (PBA) were synthesized via a precipitation method using