Oxygen Evolution Electrocatalysts with Trinuclear, Mixed‐Valence Iron Motifs on Electronically Aligned Carbon Dots

Abstract

ABSTRACT The oxygen evolution reaction (OER), a bottleneck for water electrolysis, remains limited by the adsorbate scaling relations and sluggish interfacial electron transfer (IET). We address these challenges by anchoring mixed‐valence Fe 3+ /Fe 2+ motifs on aspartic‐acid–derived carbon dots (AspCDs). Spectroscopic analyses support trinuclear Fe 3 sites, which offer redox flexibility and proximal active centers. The Fe 3 site binds the substrate (OH − ) and is electronically coupled to the AspCD scaffold. Together with the work function‐aligned scaffold for electron abstraction from OH − , these features establish effective inner‐sphere IET from OH − , through the active Fe 3 center and the AspCDs host to the electrode. Simultaneously, the mixed valency buffers the charge build‐up during the successive proton‐coupled electron transfers. The catalyst drives fast and selective O 2 generation and minimizes H 2 O 2 formation, while sustaining at least ∼70 h of continuous operation with a gradual ∼90 mV total potential increase. Thus, the Fe 3 /AspCDs catalyst requires only 110 mV overpotential at 10 mA cm −2 , shows particularly effective kinetics with a low Tafel slope of 41 mV dec −1 , and has a turnover frequency of 2.1 s −1 . The design integrates crucial physicochemical properties for highly efficient OER, and the principle can be generalized to other systems toward further advances in the field.