To solve surface carrier recombination and sluggish water oxidation kinetics of hematite (α‐Fe2O3) photoanodes, herein, an attractive surface modification strategy is developed to successively deposit ultrathin CoOx overlayer and Ni single atoms on titanium (Ti)‐doped α‐Fe2O3 (Ti:Fe2O3) nanorods through a two‐step atomic layer deposition (ALD) and photodeposition process. The collaborative decoration of ultrathin CoOx overlayer and Ni single atoms can trigger a big boost in photo‐electrochemical (PEC) performance for water splitting over the obtained Ti:Fe2O3/CoOx/Ni photoanode, with the photocurrent density reaching 1.05 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE), more than three times that of Ti:Fe2O3 (0.326 mA cm−2). Electrochemical and electronic investigations reveal that the surface passivation effect of ultrathin CoOx overlayer can reduce surface carrier recombination, while the catalysis effect of Ni single atoms can accelerate water oxidation kinetics. Moreover, theoretical calculations evidence that the synergy of ultrathin CoOx overlayer and Ni single atoms can lower the adsorption free energy of OH* intermediates and relieve the potential‐determining step (PDS) for oxygen evolution reaction (OER). This work provides an exemplary modification through rational engineering of surface electrochemical and electronic properties for the improved PEC performances, which can be applied in other metal oxide semiconductors as well.
Herein, a novel strategy of interface charge modulation for manipulating interface built-in electric fields (IEFs) and boosting spatial charge separation is introduced to alleviate charge recombination in the bulk and at the surface of hematite photoanodes. Hydrothermally grown Ti-doped hematite (Hem) nanorods are decorated with graphitic carbon nitride (g-C 3 N 4 ) species and small molybdenum oxide (MoO 3 ) clusters using a facile two-step dip-coating process. Compared with the pristine Hem, the obtained Hem/C 3 N 4 /MoO 3 exhibits increased photoelectrochemical water splitting performance with its photoanodic current density remarkably increased from 0.3 to 1.6 mA cm −2 at 1.23 V versus reversible hydrogen electrode (RHE) and incident photon-to-current conversion efficiency reaching 18.4% at 1.23 V versus RHE at 300 nm. The IEFs are introduced in the Hem/C 3 N 4 /MoO 3 heterojunction by modulating the interfacial charge property via a type II band alignment at the Hem/C 3 N 4 interface and an enhanced band bending at the surface of the photoanode, which substantially promote the spatial charge separation. By relieving the bottleneck of charge carrier transfer dynamics, this work in interfacial charge modulation provides a facile and effective strategy to boost the spatial charge separation in Hem-based photoanodes and other semiconducting devices for efficient solar energy conversion.
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