Unravelling the Interfacial Charge Dynamics of Atomically Dispersed Nickel on Hematite {001} Photoelectrodes

Abstract

The efficiency of hematite photoanodes is fundamentally constrained by sluggish kinetics and severe surface recombination, particularly on the {001} basal plane. Here, we report a defect-remediation strategy to anchor atomically dispersed Ni (AD-Ni) sites into surface states on hematite. By integrating potential sweeping and rapid thermal locking, we create an ultrathin catalytic surface that avoids the parasitic light absorption of conventional co-catalysts. The AD-Ni-engineered interfaces deliver a three-fold enhancement in photocurrent and a five-fold increase in turnover frequency (TOF) at 0.9-1.1 V vs. RHE.Intensity-modulated photocurrent spectroscopy (IMPS), combined with rate-law analysis, reveals the dual-functional role of defect-anchored Ni sites. They serve as a kinetic bridge that increases the hole transfer rate constant (ktrans) by an order of magnitude, while simultaneously passivating mid-gap states to suppress the interfacial recombination rate. This work establishes atomic-level surface engineering as a robust strategy for modulating charge dynamics and overcoming kinetic bottlenecks in earth-abundant photoelectrodes.