Transient mixed-valent Ni active sites boost urea electrooxidation

The utilization of synergistic multivalent active sites holds potential in addressing the inherent sluggish kinetics of electrocatalytic reactions. Herein, we prepared au uNPs/Ni-NDC (NDC = 1,4-Naphthalenedicarboxylic acid) and leveraged the localized surface plasmon resonance (LSPR) effect to drive hot electron transfer from au nanoparticles to the Ni substrate, thereby generating multivalent active sites to boost the urea oxidation reaction (UOR). Under exciting light, au uNPs/Ni-NDC exhibited a twofold increase in UOR current accompanied by a significant negative shift in onset potential. Operando X-ray photoelectron spectroscopy (XPS), operando X-ray absorption near edge structure (XANES) and ultrafast transient absorption (TA) spectroscopy demonstrate the formation of Ni^(3-σ)+-Ni³⁺ mixed-valent active area which driven by highly energetic electron transfer process. The density functional theory (DFT) calculations were carried out to reveal that Ni^(3-σ)+-Ni³⁺ mechanism promotes the kinetics of UOR. Urea dehydrogenation tends to occur at the Ni³⁺ sites, while *CO/*NH oxidation tends to occur at the Ni^(3-σ)+ sites.