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Defect engineering is an important method for enhancing photocatalytic performance. In article no. 1800298, Zhaowu Wang, Feng Ren, and co‐workers successfully design and prepare a defective g‐C3N4 photocatalyst via ion irradiation technology, achieving simultaneous introduction of C‐ and N‐ vacancies and the control of vacancy concentration, thus realizing a remarkable improvement in photocatalytic hydrogen production performance. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g‐C3N4) is reported to be a promising metal‐free semiconductor for photocatalytic water splitting. However, the performance of g‐C3N4 is substantially limited by its insufficient visible‐light absorption and low photogenerated charge carrier separation efficiency. In this work, an innovative method (ion irradiation) to efficiently introduce both defined C‐ and N‐vacancies (VC and VN) simultaneously into g‐C3N4 nanosheets are explored. Unlike traditional chemical methods, by controlling He+ ion fluence, tunable vacancy concentrations are able to be obtained in g‐C3N4. Defect‐engineered g‐C3N4 shows highly improved performance under optimized conditions, the defective g‐C3N4 exhibits a significantly higher (2.7‐fold) hydrogen evolution rate of 1271 µmol g−1 h−1 than that of the g‐C3N4 nanosheets under visible light (λ > 420 nm) illumination. Meanwhile, the defective g‐C3N4 exhibits a significantly enhanced (threefold) photocurrent density as photoanodes for photoelectrochemical (PEC) water splitting. Further characterizations show that the enhanced visible light absorption and an extended charge carrier lifetime, can be ascribed to the presence of C‐ and N‐ vacancies. These experimental results are in line with density functional theory (DFT) calculations. Therefore, the present work shows that defect‐engineering on g‐C3N4 using ion irradiation technique, is an effective, controllable, and defined approach to improve the photocatalytic and PEC water splitting performance of g‐C3N4. Defective g‐C3N4 photocatalysts are successfully prepared by ion irradiation technology, achieving simultaneous introduction of C– and N– vacancies and the control of vacancy concentration. The C– and N– vacancies help to enhance the absorption of visible light and the separation efficiency of photogenerated carriers, respectively, thus realizing the remarkable improvement of photocatalytic hydrogen production performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fabrication of TiO2 films by ion implantation and annealing strongly depends on ion energy. [•] Best photocatalytic activity is achieved in the TiO2 nanofilm annealed at 1000°C. [•] Phase transformation of TiO2 appears under annealing temperature of 900°C. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) is an obstacle to the electrocatalytic water splitting due to its unique four-proton-and-electron-transfer reaction process. Many methods, such as engineering heterostructure and introducing oxygen vacancy, have been used to improve the catalytic performance of electrocatalysts for OER. Herein, the above two kinds of regulation are simultaneously realized in a catalyst by using unique ion irradiation technology. A nanosheet structured NiO/NiFe 2 O 4 heterostructure with rich oxygen vacancies converted from nickel-iron layered double hydroxides by Ar + ions irradiation shows significant enhancement in both OER and hydrogen evolution reaction performance. Density functional theory (DFT) calculations reveal that the construction of NiO/NiFe 2 O 4 can optimize the free energy of O * to OOH * process during OER reaction. The oxygen vacancy-rich NiO/NiFe 2 O 4 nanosheets have an overpotential of 279 mV at 10 mA cm -2 and a low Tafel slope of 42 mV dec -1 . Moreover, this NiO/NiFe 2 O 4 electrode shows an excellent long-term stability at 100 mA cm -2 for 450 h. The synergetic effects between NiO and NiFe 2 O 4 make NiO/NiFe 2 O 4 heterostructure have high conductivity and fast charge transfer, abundant active sites, and high catalytic reactivity, contributing to its excellent performance., (© 2021 Wiley-VCH GmbH.)

Porous photoelectrodes show high efficiency in hydrogen production by water splitting. However, fabrication of porous nanorods is usually difficult. Here, we report a simple approach to fabricate a kind of novel porous rutile titanium dioxide nanorod array by an advanced ion implantation method using multiple-energy helium ion implantation and subsequent annealing. The porous nanostructure enhances the photoelectrochemical performance of the titanium dioxide nanorod array photoelectrodes under Uv-visible light illumination, where the highest photocurrent density was relatively about 10 times higher than that of the pristine titanium dioxide nanorod array. The formation of nanocavities mainly contributes to the enhancement of the photocurrent density by trapping holes inside to separate the charge carriers. The study demonstrates that ion implantation could be an effective approach to develop novel porous nanostructural photoelectrodes for the application of hydrogen production.

Mastery of the structure of nanomaterials enables control of their properties to enhance their performance for a given application. A scalable method for synthesis of alpha-Fe2O3/TiO2 bi-component nanoparticles (NPs) with novel structure (TiO2 NPs filled into the a-Fe,203) by combining with wet-chemical route and ion implantation-based physical route has been proposed. Different implanted energy and the magnetic properties of bi-component a-Fe203/TiO2 NPs were investigated. The results illustrate alpha-Fe2O3/TiO2 composite NPs can be obtained by Ti ions implantation with different energy, and the saturation magnetization (M(s)) of the samples after ion implantation are significantly enhanced. The results also reveal that conversion phase from hematite to magnetite have been occurred under the thermal effects during ion implantation.