In situ transformation of Cu₂O@MnO₂ to Cu@Mn(OH)₂ nanosheet-on-nanowire arrays for efficient hydrogen evolution

The development of new non-precious metal catalysts and understanding the origin of their activity for the hydrogen evolution reaction (HER) are essential for rationally designing highly active low-cost catalysts as alternatives to state-of-the-art precious metal catalysts. Herein, manganese oxide/hydroxide was demonstrated as a highly active electrocatalysts for the HER by fabricating MnO₂ nanosheets coated with Cu₂O nanowire arrays (Cu₂O@MnO₂ NW@NS) on Cu foam followed by an in situ chronopotentiometry (CP) treatment. It was discovered that the in situ transformation of Cu₂O@MnO₂ into Cu@Mn(OH)₂ NW@NS by the CP treatment drastically boosted the catalytic activity for the HER due to an enhancement of its intrinsic activity. Together with the benefits from such three-dimensional (3D) core–shell arrays for exposing more accessible active sites and efficient mass and electron transfers, the resulting Cu@Mn(OH)₂ NW@NS exhibited excellent HER activity and outstanding durability in terms of a low overpotential of 132 mV vs. RHE at 10 mA/cm². Overall, we expect these findings to generate new opportunities for the exploration of other Mn-based nanomaterials as efficient electrocatalysts and enable further understanding of their catalytic processes.