Chemical State Modulation of Tungsten via High-Electronegativity Nonmetallic Elements for Enhanced Electrochemical Energy Storage

Tungsten (W, 5d 4 6s 2 ), a transition metal, readily provides valence electrons during chemical reactions. Leveraging this property, this work employs a one-step hydrothermal method to introduce the strongly electronegative nonmetals oxygen (O) and selenium (Se) onto an oxidized carbon cloth (OCC) substrate, resulting in the fabrication of the electrode materials W18O49/OCC and WSe2/OCC. Material characterization and electrochemical performance analyses indicate that Se performs better in optimizing the chemical states of W, which exhibits characteristics of coexisting multiple valence states (W 4+ , W 5+ , W 6+ ). This enhances favorable sites for electron migration in subsequent electrochemical reactions, thereby improving the electrochemical performance of WSe2/OCC. Kinetic calculations reveal that the energy storage process of WSe2/OCC features both capacitive and diffusion control. Compared to W18O49/OCC, WSe2/OCC maintains a certain level of capacitive control during electrochemical reactions while allowing electrons at the liquid-solid interface and the near-surface to migrate into the bulk more easily via diffusion. This activation of internal redox reactions results in commendable performance of WSe2/OCC across a series of electrochemical tests (352.1 F g -1 at 1 A g -1 ). Furthermore, the WSe2/OCC exhibits excellent cycling stability, retaining 100 % of its initial capacitance after 10,000 cycles at 10 A g -1 , along with remarkable bending resistance.