Structural engineering and electronic state tuning optimization of molybdenum-doped cobalt hydroxide nanosheet self-assembled hierarchical microtubules for efficient electrocatalytic oxygen evolution

Abstract Cobalt-based hydroxide are ideal candidates for the oxygen evolution reaction. Herein, we use molybdenum oxide nanorods as sacrificial templates to construct a self-supporting molybdenum-doped cobalt hydroxide nanosheet hierarchical microtubule structure based on a structural engineering strategy to improve the active area of the catalyst. X-ray-based spectroscopic tests revealed that Mo (VI) with tetrahedral coordination intercalated into the interlayer of cobalt hydroxide, promoting interlayer separation. At the same time, Mo is connected with Co through oxygen bonds, which promotes the transfer of Co charges to Mo and reduces the electron cloud density of Co ions. In 1 M KOH, optimized molybdenum-doped cobalt hydroxide nanosheet microtubules only needs an overpotential of 288 mV to drive a current density of 10 mA cm⁻², which is significantly better than that of pure Co(OH)₂ nanosheets and RuO2. Structural engineering and electronic state regulation can effectively improve the oxygen evolution activity of cobalt-based hydroxide, which provides a design idea for the development of efficient oxygen evolution catalysts

Mass-production of mesoporous MnCo₂O₄ spinels with manganese(IV)- and cobalt(II)-rich surfaces for superior bifunctional oxygen electrocatalysis

Abstract A mesoporous MnCo₂O₄ electrode material is made for bifunctional oxygen electrocatalysis. The MnCo₂O₄ exhibits both Co₃O₄-like activity for oxygen evolution reaction (OER) and Mn₂O₃-like performance for oxygen reduction reaction (ORR). The potential difference between the ORR and OER of MnCo₂O₄ is as low as 0.83 V. By XANES and XPS investigation, the notable activity results from the preferred MnIV- and CoII-rich surface. The electrode material can be obtained on large-scale with the precise chemical control of the components at relatively low temperature. The surface state engineering may open a new avenue to optimize the electrocatalysis performance of electrode materials. The prominent bifunctional activity shows that MnCo₂O₄ could be used in metal–air batteries and/or other energy devices