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Developing highly efficient, low cost, and stable electrocatalysts that work at a large current density is crucial for upgrading the current industrial electrochemical water splitting to produce H2. Molybdenum selenide (MoSe2) is a promising 2D transition metal dichalcogenide (TMD), however, its reported output is inadequate due to its inert basal plane. Herein, the catalytic activity of MoSe2 nanosheet arrays is activated by a novel and controllable method of He+ ion irradiation to introduce multiple vacancies simultaneously into their inert basal planes. The vacancies activated MoSe2 have improved electrocatalytic performance and stability with a minimum overpotential of 90 mV at 10 mA cm−2, a Tafel slope of 49 mV dec−1 and high stability of 650 h at the industry‐level large current density of 1000 mA cm−2 compared to several hours for the pristine sample. The DFT results reveal that single Se and single Mo vacancies on the MoSe2 basal plane can efficiently increase the electrical conductivity and reduce energy barriers for water dissociation and subsequent proton adsorption, thus improving the electrocatalytic capability. This finding proves the application of ion beam in defect engineering for effective hydrogen evolution in TMDs‐based catalysts. [ABSTRACT FROM AUTHOR]

• A unique ion irradiation method was used to fabricate the OER catalyst. • The ir-S-NiO catalyst exhibits improved performance and long-term life for OER. • The sulfate modification accelerated the surface reconstruction. • Oxygen vacancies and sulfate regulated the electronic structure of catalyst. NiO has attracted wide attention in the past decade as a cost-effective electrochemical catalyst for OER. However, its relatively poor performance and conductivity limit its commercial applications. Here, we highlight a unique ion irradiation method to enhance the catalytic activity of NiO. Benefiting from sulfate anchoring and the introduction of oxygen vacancies by He+ ion irradiation, the optimal catalyst (ir-S-NiO) exhibits an outstanding OER performance with a low overpotential of 269 mV at 10 mA cm−2. Moreover, the fabricated Anion exchange membrane water electrolyzer (AEMWE) constructed by the ir-S-NiO is demonstrated to need a cell voltage of 1.72 V to reach a current density of 0.1 A cm−2 and shows remarkably long-term stability for 200 h without obvious attenuation at the current density of 0.5 A cm−2. This work provides a new method for the development of high-performance and stable OER electrocatalysts. [ABSTRACT FROM AUTHOR]

In this work, well-ordered nanorods were fabricated on the surface of TiO 2 thin films deposited on Ti sheets by an ion irradiation method using nitrogen ion irradiation with the energy of 65 keV to a fluence of 1 × 10 17 ions/cm 2 . These TiO 2 nanorods are about 120 nm in length and 20–40 nm in diameter. After post-irradiation annealing at 500 °C in O 2 , the nanorod array photoelectrode displays largely enhanced performance for photoelectrochemical (PEC) water splitting compared to that of the un-irradiated TiO 2 thin films with a planar structure. The influences of the irradiated ion energy on the morphology and photocurrent density of the nanorods were investigated. The 65 keV N + irradiated TiO 2 thin films shows a higher photocurrent density than those of the 45 and 85 keV N + irradiated TiO 2 thin films. We also discussed the influence of annealing conditions on the PEC performance of TiO 2 nanorods, and it was found that the nanorods annealed at 600 °C in vacuum produce a much higher photocurrent density of 0.6 mA/cm 2 at 0.8 V (vs. a saturated calomel electrode), which is about 7 times higher than that of the nanorods annealed in oxygen. This work proposes that ion irradiation combination with thermal annealing in vacuum could be an effective approach for developing nanostructured materials for water splitting. [ABSTRACT FROM AUTHOR]