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Although much effort has been devoted to improving photoelectrochemical water splitting of hematite (α-Fe2O3) due to its high theoretical solar-to-hydrogen conversion efficiency of 15.5%, the low applied bias photon-to-current efficiency remains a huge challenge for practical applications. Herein, we introduce single platinum atom sites coordination with oxygen atom (Pt-O/Pt-O-Fe) sites into single crystalline α-Fe2O3 nanoflakes photoanodes (SAs Pt:Fe2O3-Ov). The single-atom Pt doping of α-Fe2O3 can induce few electron trapping sites, enhance carrier separation capability, and boost charge transfer lifetime in the bulk structure as well as improve charge carrier injection efficiency at the semiconductor/electrolyte interface. Further introduction of surface oxygen vacancies can suppress charge carrier recombination and promote surface reaction kinetics, especially at low potential. Accordingly, the optimum SAs Pt:Fe2O3-Ov photoanode exhibits the photoelectrochemical performance of 3.65 and 5.30 mA cm−2 at 1.23 and 1.5 VRHE, respectively, with an applied bias photon-to-current efficiency of 0.68% for the hematite-based photoanodes. This study opens an avenue for designing highly efficient atomic-level engineering on single crystalline semiconductors for feasible photoelectrochemical applications. The achievable photocurrent of hematite, α-Fe2O3, is typically limited far below its theoretical limit. Here, the authors engineer single Pt atomic sites with surface oxygen vacancies into hematite photoanodes, which leads to enhanced photoelectrochemical water splitting. [ABSTRACT FROM AUTHOR]

Photostability is one of the most essential properties for evaluating photoelectrochemical (PEC) water splitting performance on semiconductors. Herein, the oxygen‐deficiency conditions are applied to tune and activate BiVO4 photoanodes with a class of oxygen vacancies across the whole bulk material, and regulate the electronic occupancy of these states upon the charge carrier processes that determine PEC water oxidation activity. Through the experimental results and nonadiabatic molecular dynamics with time‐domain density functional theory calculations, the charge carrier lifetime can be influenced by the oxygen vacancies concentration on BiVO4, and the semiconductor can be flexibly photoactivated under oxygen‐sufficient and deficient atmospheres for enhancing the charge carrier density and photovoltage. The PEC performance of BiVO4 is further boosted by Pt doping, which exhibits a record photocurrent density of 5.45 mA cm–2 at 1.23 VRHE with solar conversion efficiency of 2.1% at 0.65 VRHE. The Pt can prevent the unnecessory charge recombination on the defected BiVO4, which also enhances the majority charge carrier density, resulting in one of the best charge separation efficiencies, close to 100%, among the steady‐state PEC performance for BiVO4. More importantly, the resulting Pt:BiVO4 presents long‐term stability over 50 h at 0.8 VRHE. [ABSTRACT FROM AUTHOR]

A photocharge/discharge strategy is proposed to initiate the WO3 photoelectrode and suppress the main charge recombination, which remarkably improves the photoelectrochemical (PEC) performance. The photocharged WO3 surrounded by a 8–10 nm overlayer and oxygen vacancies could be operated more than 25 cycles with 50 h durability without significant decay on PEC activity. A photocharged WO3/CuO photoanode exhibits an outstanding photocurrent of 3.2 mA cm−2 at 1.23 VRHE with a low onset potential of 0.6 VRHE, which is one of the best performances of p‐n heterojunction structure. Using nonadiabatic molecular dynamics combined with time‐domain DFT, we clarify the prolonged charge carrier lifetime of photocharged WO3, as well as how electronic systems of photocharged WO3/CuO semiconductors enable the effective photoinduced electrons transfer from WO3 into CuO. This work provides a feasible route to address excessive defects existed in photoelectrodes without causing extra recombination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergy effects of gradient Nb doping and bulk Mo doping boost WOR performances. • First introduction of Nb into BiVO 4 photoelectrodes with highly effective WOR. • G-Nb/Mo:BVO presents an average Faraday efficiency of 80% for H 2 O 2 production. • G-Nb/Mo:BVO achieves the best H 2 O 2 production rate of 1.23 μmol min−1 cm−2. • Heterogeneous doping improves water oxidation reaction activity and selectivity. Photoelectrochemical (PEC) water splitting into H 2 O 2 and H 2 has attracted significant attention due to its low cost and sustainability. However, slow charge carrier transport and water oxidation kinetics limit the selectivity for H 2 O 2 production and solar conversion efficiency. Herein, we propose a heterogeneous doping approach that combines surface gradient doping with bulk doping to improve the charge carrier transport in the photoelectrode. Inducing gradient Nb and homogeneous Mo doping into BiVO 4 photoanode (G-Nb/Mo:BVO) can promote charge separation and carrier transfer, leading to the high selectivity for H 2 O 2 generation and suppression of O 2 production. Consequently, the heterogeneously doped G-Nb/Mo:BVO photoanode presents an average Faraday efficiency (FE) of over 80% for H 2 O 2 production in a wide potential of 0.6–1.8 V RHE with the maximum FE of 83.7% at 1.2 V RHE under AM 1.5G illumination. More importantly, H 2 O 2 production rate can reach 1.23 μmol min−1 cm−2 at 1.23 V RHE , representing the best H 2 O 2 production rate reported for the photoelectrodes. Density functional theory calculations prove that Mo and Nb co-doping increases the reactivity of BiVO 4 and improves 2e− water oxidation reaction activity and selectivity. This work demonstrates that heterogeneous doping provides a cost-effective strategy to break performance trade-offs by improving charge carrier separation and transport in light absorbers, and modulating the selectivity and activity of water oxidation reaction to generate H 2 O 2 , which can be extended to other photocatalytic reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gradient Ce doping on Fe 2 O 3 with the construction of built-in electric field. • Surface polarization on gradient Ce doped Fe 2 O 3 reduced the interfacial oxygen vacancies. • The photoanode exhibited a photocurrent of 2.50 mA cm−2 at 1.50 V RHE with a low onset potential of 0.64 V RHE. • DFT calculations demonstrated the elimination of deep trap state and the reduction of charge recombination. Photoelectrochemical (PEC) water splitting is one of the most strategies for solar energy storage and utilization. Hematite as one of the promising candidates for PEC research, has a short hole diffusion length and short carrier lifetime, resulting in PEC conversion efficiency far below the theoretical value. In this work, a facile but efficient strategy was introduced for the growth of gradient Ce doped hematite nanorods, following with the sequent photoactivation process. The gradient Ce doping not only increased the conductivity of bulk material, but also importantly, constructed a built-in electric field by the addition of Ce element, which remarkably enhanced the charge separation and transfer from the bulk to the surface. Moreover, the surface polarization under illumination was applied for the reduction of overpotential and the enhancement of photocurrent density, taking a role of cocatalyst decoration. It reduced the oxygen vacancies concentration at the surface, which further reduced the surface recombination owing to the passivation from photoactivation. According to these, the resulting photoanode exhibited a photocurrent of 1.92 and 2.50 mA cm−2 at 1.23 and 1.50 V RHE , respectively, with onset potential of 0.64 V RHE under AM 1.5G illumination. This work opens a useful strategy of modifying the electronic structure and constructing the interface structure for improving PEC performance on hematite-based photoelectrodes for solar energy storage and utilization. [ABSTRACT FROM AUTHOR]