Field-Effect Enhancement of Non-Faradaic Processes at Interfaces Governs Electrocatalytic Water Splitting Activity

Recognizing the essential factor governing interfacial hydrogen/oxygen evolution reactions (HER/OER) is central to electrocatalytic water-splitting. Traditional strategies aiming at enhancing electrocatalytic activities have mainly focused on manipulating active site valencies or coordination environments. Herein, the role of interfacial adsorption is probed and modulated by the topological construct of the electrocatalyst, a frequently underestimated non-Faradaic mechanism in the dynamics of electrocatalysis. The engineered Co_0.75Fe_0.25P nanorods, anchored with FeO_x clusters, manifest a marked amplification of the surface electric field, thus delivering a substantially improved bifunctional electrocatalytic performance. In alkaline water splitting anion exchange membrane (AEM) electrolyzer, the current density of 1.0 A cm^-2 can be achieved at a cell voltage of only 1.73 V for the FeO_x@Co_0.75Fe_0.25P|| FeO_x@Co_0.75Fe_0.25P pairs for 120 h of continuous operation at 1.0 A cm^-2. Detailed investigations of electronic structures, combined with valence state and coordination geometry assessments, reveal that the enhancement of catalytic behavior in FeO_x@Co_0.75Fe_0.25P is chiefly attributed to the strengthened adsorptive interactions prompted by the intensified electric field at the surface. The congruent effects observed in FeO_x-cluster-decorated Co_0.75Fe_0.25P nanosheets underscore the ubiquity of this effect. The results put forth a compelling proposition for leveraging interfacial charge densification via deliberate cluster supplementation.