Angga Hermawan, Nahdori Muhlis, Suci Winarsih, Joko Suwardy, Fadli Rohman, Andri Hardiansyah, Ni Luh Wulan Septiani, Vinda Puspasari, Sri Kadarwati, Shu Yin
We report a polymerizable-complex synthesis that achieves, to the best of our knowledge, the highest Mn substitution level reported within a single-phase fluorite Ce1-xMnxO2 structure prepared by solution-based synthesis. Mixing Ce and Mn precursors at the molecular level yields single-phase Ce1-xMnxO2 solid solutions up to x = 0.7 (70 at.%), beyond which phase separation into Mn3O4 occurs. Progressive Mn incorporation causes systematic lattice contraction, dramatic crystallite refinement (down to ≈1 nm), elevated Ce3+ fraction and an increased concentration of oxygen vacancies as evidenced by XRD, XPS and Raman analyses. These defect and electronic-structure modifications reduce the optical band gap, enhance surface area and create abundant redox-active centers that boost charge storage. In three-electrode testing (1 M Na2SO4) the Ce0.3Mn0.7O2 electrode attains a specific capacitance of ≈203 F g−1 at 0.5 A g−1 and shows mixed capacitive/pseudocapacitive behaviour with superior low-rate performance; more Mn-rich compositions trade some capacity for improved rate capability. When paired with water-hyacinth derived activated carbon in a mass-balanced asymmetric device (WHAC || Ce0.3Mn0.7O2) operating at 2.0 V in neutral 1 M Na2SO4, the device achieves a peak energy density of 33.1 Wh kg−1 at 1000 W kg−1 and retains 77.2% capacity after 10,000 cycles with ~98–100% coulombic efficiency. Our results establish polymerizable-complex chemistry as a versatile route to extreme dopant incorporation in fluorite oxides and identify highly Mn-substituted CeO2 as a defect-engineered electrode material that combines high energy, aqueous safety and long-term stability. © 2026 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Research Center for Nanotechnology System, National Research and Innovation Agency (BRIN), Banten, South Tangerang City, 15314, Indonesia; Department of Chemistry, Faculty of Mathematics and Natural Science, Universitas Negeri Semarang, Central Java, Semarang, 50229, Indonesia; Research Center for Quantum Physics, National Research and Innovation Agency (BRIN), Banten, South Tangerang City, 15314, Indonesia; Research Center for Energy Materials, National Research and Innovation Agency (BRIN), Banten, South Tangerang City, 15314, Indonesia; Research Center for Electronics, National Research and Innovation Agency (BRIN), Jawa Barat, Bandung, 40135, Indonesia; Research Center for Metallurgy, National Research and Innovation Agency (BRIN), Banten, South Tangerang City, 15314, Indonesia; Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Miyagi, Sendai, 980-8577, Japan; Advance Institute for Materials Research (WPI-AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Miyagi, Sendai, 980-8577, Japan
