Operando Identification of Ni dz ² Orbital Descriptor Governing Urea Oxidation Electrocatalysis

ABSTRACT

Electrocatalytic urea oxidation reaction (UOR) offers a low‐thermodynamic‐potential alternative to the oxygen evolution reaction, yet the true reactive state of nickel and a quantitative electronic descriptor governing activity remain unresolved. Here, we construct a well‐defined catalyst–support interaction platform that enables dynamic regulation of the Ni 3d electronic structure through π–π coupling between nickel phthalocyanine (NiPc) and carbon supports with tunable curvature. Crucially, operando x‐ray absorption spectroscopy, Kβ x‐ray emission spectroscopy, and high‐energy‐resolution fluorescence‐detected XAS unambiguously demonstrate that enhanced UOR activity originates from dynamic redistribution of Ni 3d orbitals rather than oxidation‐state evolution, thereby resolving a long‐standing controversy in Ni‐based catalysis. The operando results further confirm that Ni ²⁺ remains the catalytically active state throughout the reaction and identify the occupancy of the 3dz ² orbital as a quantitative electronic descriptor governing intrinsic activity. NiPc supported on 2 nm carbon nanotubes achieves a turnover frequency of 1.67 s ⁻¹ at 1.45 V versus RHE, outperforming its planar and weakly interacting counterparts, in which strong interfacial interaction induces a high‐spin Ni(II) configuration with a nearly half‐filled 3dz ² orbital. This study establishes operando‐validated frontier orbital engineering via catalyst–support interactions as a rational strategy for advanced electrocatalyst design.