Radiation-induced in situ synthesis of Ni anchored MoO₃ with oxygen vacancy for high-performance pseudocapacitor

Introduction of active centers, such as oxygen vacancy and metal single atoms, has emerged as a promising strategy to further improve the electrochemical properties of transition metal oxide electrodes for high-performance pseudocapacitors. Here, an unprecedented MoO₃ with multiple active centers, Ni anchored reduced MoO₃ with oxygen vacancy (Ni-rMoO_3−x), was in situ synthesized via γ-ray radiation-induced one-pot strategy under ambient conditions. This approach leverages the synergistic effects of radiation activation, etching, and reduction. The characteristics of multiple valence states (Mo^4+/5+/6+ and Ni^0/2+), oxygen vacancies, single atoms, and atomic clusters in Ni-rMoO_3−x were determined by X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure spectroscopy (XAFS), and atomic-resolution aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements. Notably, Ni-rMoO_3−x exhibited exceptional pseudocapacitive performance, with ultrahigh specific charge (881.0 C·g⁻¹ at 1 A·g⁻¹, more than twice that of MoO₃), fast charge/discharge rates, and remarkable cycle life stability (98.5% capacitance retention after 10,000 cycles). Furthermore, a hybrid supercapacitor device (Ni-rMoO_3−x//activated carbon (AC)) demonstrated a high energy density of 97.8 Wh·kg⁻¹ at a power density of 0.90 kW·kg⁻¹ and exhibited excellent mechanical flexibility for practical applications.