A facile approach to tailor electrocatalytic properties of MnO2 through tuning phase transition, surface morphology and band structure

The structural and electronic properties of MnO2 based electrocatalysts are key factors determining their electrochemical performance. To date, it is still challenging to synergistically tune the crystal structure, morphology, and electronic band (i.e., band gap and band alignments) of MnO2 through facile synthesis approaches. This study has reported a one-step hydrothermal method to synthesize a prototypical MnO2 electrocatalyst with optimized structural and electrochemical properties. By simply adjusting the hydrothermal time, the phase transition from polymorphic 8 to alpha can be induced in MnO2. The obtained nanowires on nanosheets structure grown in-situ on nickel foam provides a large surface area, great accessible active sites, and good mass/charge transfer efficiency. Further investigation through first-principles calculations reveals that compared to delta-MnO2, the alpha-MnO2 polymorph with rich oxygen vacancies has better band-alignment tunability, which is also beneficial for improving the electrochemical performance. The alpha phase MnO2 exhibits superior catalytic performance for both OER and HER (OER overpotential of 0.45 V at 50 mA cm(-2) and HER overpotential of 0.14 V at 50 mA cm(-2)). The developed synthesis method can be extended to catalyst designs that require precise control of phase and morphology evolution in a wide range of applications.

Automated summary

This study presents a hydrothermal method for synthesizing MnO2 electrocatalysts with optimized structural and electrochemical properties. By adjusting the hydrothermal time, the phase transition from polymorphic 8 to alpha-MnO2 can be induced. The alpha-MnO2 polymorph with oxygen vacancies shows better band-alignment tunability, leading to improved electrochemical performance.