Atomic layers of ruthenium oxide coupled with Mo₂TiC₂T_x MXene for exceptionally high catalytic activity toward water oxidation

Progress in acidic water splitting has remained limited because of low oxygen evolution reaction (OER) activities, sluggish reaction kinetics, and severe catalyst degradation. Thus, a highly active and durable OER catalyst is required for the commercialization of acidic water electrolyzers. Here, we report t-phase ruthenium oxide atomic layers implanted on Mo₂TiC₂T_x MXene (R_AL-M) as a model electrocatalyst for the OER in acidic media, which exhibits a remarkable mass activity (6.2 A mg⁻¹), excellent turnover frequency (TOF; 2.4 s⁻¹), and negligible loss of durability after 22 h in a two-electrode cell configuration. The mass activity and TOF of R_AL-M are 150 times (RuO₂-Premetek Co.) and 540 times (RuO₂-Sigma-Aldrich) greater than the industrially adopted electrocatalysts at pH 0.48. Computational calculations show that the ruthenium active sites of R_AL-M have a strong affinity to oxygen species (e.g., OH*, O*, and OOH*), which efficiently adapts water dissociation and favors both the adsorbate evolution and lattice oxygen mechanistic pathways to accelerate the OER.