To exploit the full potential of hematite (α-FeO) as an efficient photoanode for water oxidation, the redox processes occurring at the FeO/electrolyte interface need to be studied in greater detail. Ex situ doping is an excellent technique to introduce dopants onto the photoanode surface and to modify the photoanode/electrolyte interface. In this context, we selected antimony (Sb) as the ex situ dopant because it is an effective electron donor and reduces recombination effects and concurrently utilize the possibility to tuning the surface charge and wettability. In the presence of Sb states in Sb-doped FeO photoanodes, as confirmed by X-ray photoelectron spectroscopy, we observed a 10-fold increase in carrier concentration (1.1 × 10 vs 1.3 × 10 cm) and decreased photoanode/electrolyte charge transfer resistance (∼990 vs ∼3700 Ω). Furthermore, a broad range of surface characterization techniques such as Fourier-transform infrared spectroscopy, ζ-potential, and contact angle measurements reveal that changes in the surface hydroxyl groups following the ex situ doping also have an effect on the water splitting capability. Theoretical calculations suggest that Sb can activate multiple Fe ions simultaneously, in addition to increasing the surface charge and enhancing the electron/hole transport properties. To a greater extent, the Sb- surface-doped determines the interfacial properties of electrochemical charge transfer, leading to an efficient water oxidation mechanism.

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Engineering the electronic properties of transition metal phosphides has shown great effectiveness in improving their intrinsic catalytic activity for the hydrogen evolution reaction (HER) in water splitting applications. Herein, we report for the first time, the creation of Fe vacancies as an approach to modulate the electronic structure of iron phosphide (FeP). The Fe vacancies were produced by chemical leaching of Mg that was introduced into FeP as “sacrificial dopant”. The obtained Fevacancy‐rich FeP nanoparticulate films, which were deposited on Ti foil, show excellent HER activity compared to pristine FeP and Mg‐doped FeP, achieving a current density of 10 mA cm−2 at overpotentials of 108 mV in 1 m KOH and 65 mV in 0.5 m H2SO4, with a near‐100 % Faradaic efficiency. Our theoretical and experimental analyses reveal that the improved HER activity originates from the presence of Fe vacancies, which lead to a synergistic modulation of the structural and electronic properties that result in a near‐optimal hydrogen adsorption free energy and enhanced proton trapping. The success in catalytic improvement through the introduction of cationic vacancy defects has not only demonstrated the potential of Fe‐vacancy‐rich FeP as highly efficient, earth abundant HER catalyst, but also opens up an exciting pathway for activating other promising catalysts for electrochemical water splitting.

The metastable 1T′ polymorph of molybdenum disulfide (MoS 2 ) has shown excellent catalytic activity toward the hydrogen evolution reaction (HER) in water-splitting applications. Its basal plane exhibits high catalytic activity comparable to the edges in 2H MoS 2 and noble metal platinum. However, the production and application of this polymorph are limited by its lower energetic stability compared to the semiconducting 2H MoS 2 phase. Here, the production of stable intercalated 1T′ MoS 2 nanosheets attached on graphitic nanoribbons is reported. The intercalated 1T′ MoS 2 exhibits a stoichiometric S:Mo ratio of 2.3 (±0.1):1 with an expanded interlayer distance of 10 Å caused by a sulfur-rich intercalation agent and is stable at room temperature for several months even after drying. The composition, structure, and catalytic activity toward HER are investigated both experimentally and theoretically. It is concluded that the 1T′ MoS 2 phase is stabilized by the intercalated agents, which further improves the basal planes′ catalytic activity toward HER.of stable sulfur-intercalated 1T′ MoS 2 and also gives some perspective for producing stable 1T′ polymorphs of other layered transition metal dichalcogenides.The authors declare no conflict of interest.

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