The pathway of the oxygen evolution reaction at the Pt(1 1 1)/water interface is disclosed through constant Fermi level molecular dynamics. Upon the application of a positive bias potential H2O_ads and O_ads adsorbates are found to arrange in a hexagonal lattice with an irregular alternation. Increasing further the electrode potential then induces the oxygen evolution reaction, which is found to proceed through a hydrogen peroxide intermediate. Calculation of the associated overpotential shows a reduction of 0.2 eV compared to the associative mechanism. This result highlights the forcefullness of the applied scheme in exploring catalytic reactions in an unbiased way.