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 δ to α can be induced in MnO₂. The obtained nanowires on nanosheet 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 δ-MnO_2, the α-MnO₂ polymorph with rich oxygen vacancies has better band-alignment tunability, which is also beneficial for improving the electrochemical performance. The α 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.

_{MnO 2}基电催化剂的结构和电子性质是决定其电化学性能的关键因素。迄今为止，通过简便的合成方法协同调整MnO _{2的晶体结构、形态和电子能带（即带隙和能带排列）仍然具有挑战性。}本研究报道了一种一步水热法合成具有优化结构和电化学性能的原型MnO _{2电催化剂。}通过简单地调节水热时间，可以在 MnO _{2中诱导多晶型 δ 到 α 的相变}. 在泡沫镍上原位生长的纳米片结构上获得的纳米线提供了大的表面积、可接近的活性位点和良好的质量/电荷转移效率。通过第一性原理计算进一步研究表明，与δ-MnO _{2 相比，}具有丰富氧空位的α-MnO ₂多晶型具有更好的能带排列可调性，这也有利于提高电化学性能。α 相 MnO ₂对 OER 和 HER 均表现出优异的催化性能（OER 过电位为 0.45 V 在 50 mA cm ^–2和 HER 过电位为 0.14 V 在 50 mA cm ^–2）。开发的合成方法可以扩展到需要在广泛的应用中精确控制相和形态演变的催化剂设计。