2 research outputs found
δ‑MnO<sub>2</sub>–Mn<sub>3</sub>O<sub>4</sub> Nanocomposite for Photochemical Water Oxidation: Active Structure Stabilized in the Interface
Pure phase manganese oxides have
been widely studied as water oxidation
catalysts, but further improvement of their activities is much challenging.
Herein, we report an effective method to improve the water oxidation
activity by fabricating a nanocomposite of Mn<sub>3</sub>O<sub>4</sub> and δ-MnO<sub>2</sub> with an active interface. The nanocomposite
was achieved by a partial reduction approach which induced an in situ
growth of Mn<sub>3</sub>O<sub>4</sub> nanoparticles from the surface
of δ-MnO<sub>2</sub> nanosheets. The optimum composition was
determined to be 38% Mn<sub>3</sub>O<sub>4</sub> and 62% δ-MnO<sub>2</sub> as confirmed by X-ray photoelectron spectra (XPS) and X-ray
absorption spectra (XAS). The δ-MnO<sub>2</sub>–Mn<sub>3</sub>O<sub>4</sub> nanocomposite is a highly active water oxidation
catalyst with a turnover frequency (TOF) of 0.93 s<sup>–1</sup>, which is much higher than the individual components of δ-MnO<sub>2</sub> and Mn<sub>3</sub>O<sub>4</sub>. We consider that the enhanced
water oxidation activity could be explained by the active interface
between two components. At the phase interface, weak Mn–O bonds
are introduced by lattice disorder in the transition of hausmannite
phase to birnessite phase, which provides active sites for water oxidation
catalysis. Our study illustrates a new view to improve water oxidation
activity of manganese oxides
A Graphene-like Oxygenated Carbon Nitride Material for Improved Cycle-Life Lithium/Sulfur Batteries
Novel sulfur (S) anchoring materials
and the corresponding mechanisms for suppressing capacity fading are
urgently needed to advance the performance of Li/S batteries. Here,
we designed and synthesized a graphene-like oxygenated carbon nitride
(OCN) host material that contains tens of micrometer scaled two-dimensional
(2D) rippled sheets, micromesopores, and oxygen heteroatoms. N content
can reach as high as 20.49 wt %. A sustainable approach of one-step
self-supporting solid-state pyrolysis (OSSP) was developed for the
low-cost and large-scale production of OCN. The urea in solid sources
not only provides self-supporting atmospheres but also produces graphitic
carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) working as 2D layered
templates. The S/OCN cathode can deliver a high specific capacity
of 1407.6 mA h g<sup>–1</sup> at C/20 rate with 84% S utilization
and retain improved reversible capacity during long-term cycles at
high current density. The increasing micropores, graphitic N, ether,
and carboxylic O at the large sized OCN sheet favor S utilization
and trapping for polysulfides