Nonmetallic Active Sites on Nickel Phosphide in Oxygen Evolution Reaction

Abstract

Efficient and durable catalysts are crucial for the oxygen evolution reaction (OER). The discovery of the high OER catalytic activity in Ni12P5 has attracted a great deal of attention recently. Herein, the microscopic mechanism of OER on the surface of Ni12P5 is studied using density functional theory calculations (DFT) and ab initio molecular dynamics simulation (AIMD). Our results demonstrate that the H2O molecule is preferentially adsorbed on the P atom instead of on the Ni atom, indicating that the nonmetallic P atom is the active site of the OER reaction. AIMD simulations show that the dissociation of H from the H2O molecule takes place in steps; the hydrogen bond changes from Oa-H⋯Ob to Oa⋯H-Ob, then the hydrogen bond breaks and an H+ is dissociated. In the OER reaction on nickel phosphides, the rate-determining step is the formation of the OOH group and the overpotential of Ni12P5 is the lowest, thus showing enhanced catalytic activity over other nickel phosphides. Moreover, we found that the charge of Ni and P sites has a linear relationship with the adsorption energy of OH and O, which can be utilized to optimize the OER catalyst.

The Role of Hydrogen Adsorption Site Diversity in Catalysis on Transition-Metal Phosphide Surfaces

“…On a metal surface, the dissociation of H 2 is more likely to proceed via homolytic bond cleavage due to identical (or near identical) adsorption sites for the H atom. On a TMP surface, H 2 is more likely to be cleaved heterolytically, similar to what is observed on other binary materials. − A surface consisting of metal and phosphorus induces inhomogeneous surface electron density , that may favor heterolytic cleavage by polarizing the H 2 bond. A recent computational study further shows that the H 2 dissociation mechanism may be termination-dependent on metal-doped Ni 2 P .…”

“…On a TMP surface, H 2 is more likely to be cleaved heterolytically, similar to what is observed on other binary materials. 71−73 A surface consisting of metal and phosphorus induces inhomogeneous surface electron density 74,75 that may favor heterolytic cleavage by polarizing the H 2 bond. A recent computational study further shows that the H 2 dissociation mechanism may be termination-dependent on metal-doped Ni 2 P. 76 Regardless of the mechanism, the adsorption site diversity results in the presence of H ad with various HBEs on TMP surfaces after exposure to H 2 .…”

Highly Porous Carbon Flakes Derived from Cellulose and Nickel Phosphide Heterostructure towards Efficient Electrocatalysis of Oxygen Evolution Reaction

“…Nevertheless, throughout the process, the phosphorus atoms carry a higher positive charge compared to nickel, facilitating the easier adsorption of OH − in the initial reaction. This characteristic contributes to an overall enhancement in the efficiency of the OER process [ 57 ]. By combining Ni 12 P 5 with other elements, Ni atoms receive a partial electron from another element, which may result in a decrease in the adsorption energies of reaction intermediates [ 58 ].…”

The Role of Hydrogen Adsorption Site Diversity in Catalysis on Transition Metal Phosphide Surfaces

“…On a TMP surface, H2 is more likely to be cleaved heterolytically, similar to what is observed on other binary materials. [71][72][73] A surface consisting of metal and phosphorus induces inhomogeneous surface electron density 74,75 that may favor heterolytic cleavage by polarizing the H2 bond. A recent computational study further shows that the H2 dissociation mechanism may be termination-dependent on metal-doped Ni2P.…”