Cost-effective ion-tuning of Birnessite structures for efficient ORR electrocatalysts

Opposite Effects of Co and Cu Dopants on the Catalytic Activities of Birnessite MnO2 Catalyst for Low-Temperature Formaldehyde Oxidation

“…Similar observations were reported for Cu-doped δ-MnO 2 for toluene and benzene oxidation, with significantly lower temperature activities compared to the unmodified δ-MnO 2 , owing to the formation of oxygen vacancies and its resultant effect on low-temperature reducibility and lattice oxygen reactivity. Doping Cu into the octahedra framework of δ-MnO 2 was also shown to reduce the electron-transfer resistance of δ-MnO 2 , thereby enhancing its catalytic activity and stability for oxygen reduction reaction . The above works have demonstrated the prospects of Co and Cu as suitable dopants for enhancing the properties and catalytic activity of δ-MnO 2 for HCHO oxidation, as defective sites were demonstrated to improve the redox properties of Mn and facilitate the activation and mobility of oxygen into surface active species, which in turn enhances the catalytic activity for HCHO. ,, …”

“…Doping Cu into the octahedra framework of δ-MnO 2 was also shown to reduce the electron-transfer resistance of δ-MnO 2 , thereby enhancing its catalytic activity and stability for oxygen reduction reaction. 14 The above works have demonstrated the prospects of Co and Cu as suitable dopants for enhancing the properties and catalytic activity of δ-MnO 2 for HCHO oxidation, as defective sites were demonstrated to improve the redox properties of Mn and facilitate the activation and mobility of oxygen into surface active species, which in turn enhances the catalytic activity for HCHO. 8,22,23 Besides the enhancement of catalysts' properties induced by doping, the influence of dopants on the surface reaction of intermediates is another critical parameter that influences catalytic activity.…”

“…7,[11][12] Additionally, dopants can improve the catalytic activity of δ-MnO2 by enhancing its redox properties and lattice oxygen mobility and reactivity through the reduction of charge transfer resistance. [13][14] Due to their similar ionic radii, Cobalt (Co) was shown to effectively incorporate into the octahedra of δ-MnO2 by substituting Mn 4+ leading to the creation oxygen vacancies. 10 Elmaci et al 13 explored various transition metals as dopants for δ-MnO2 and demonstrated that, compared to the pristine δ-MnO2, Co-doped δ-MnO2 exhibited enhanced catalytic activity and chemical stability for water oxidation reaction.…”

“…Structural defects could be induced through doping or the incorporation of metal cations into the lattice framework of the host material. , The partial substitution of Mn 4+ by dopants within the [MnO 6 ] octahedral framework of δ-MnO 2 could lead to the generation of oxygen vacancies and structural lattice distortion . These defective sites serve as centers for the adsorption and activation of molecules, and in particular, the generation of active oxygen species, through the activation of water and/or molecular oxygen, which were shown to actively participate in most oxidation reactions, particularly HCHO oxidation. ,, Additionally, dopants can improve the catalytic activity of δ-MnO 2 by enhancing its redox properties and lattice oxygen mobility and reactivity through the reduction of charge transfer resistance. , …”