Structure engineering of MoO₃ breaks the scaling relationship and achieves high electrocatalytic oxygen evolution activity in acidic conditions

Developing high-efficiency and low-cost electrocatalysts for the oxygen evolution reaction (OER) is needed for sustainable fuel production and energy storage. However, the inherent scaling relationship in the conventional adsorbate evolution mechanism (AEM) limits the development of electrocatalysts. In this work, the effects of alkali metals (AM = Li, Na, K, or Cs) and substitutional transition metals (TMs = Fe, Co, Ni, Ru, or Ir) on the electrocatalytic OER activity of the MoO3 monolayer were investigated. AM modification is an effective way to dislodge the inertia of MoO3 for access to acceptable overpotentials (<0.5 V), whereas the inevitable oxygen vacancy counteracted the promotion effect of AMs and even worsened the reaction kinetics. Interestingly, 3d-TM doping changed the reaction mechanism from the conventional AEM to the novel lattice oxygen mechanism (LOM), and removed the theoretical overpotential limitation (0.3-0.4 V), and AM modification improved the lattice oxygen reactivity further by adjusting the p-band centre. Co-MoO3(Na) showed optimum OER activity with a very low overpotential of 0.19 V.