Solution-based ZnO nanorod arrays (NRAs) were modified with controlled N doping by an advanced ion implantation method, and were subsequently utilized as photoanodes for photoelectrochemical (PEC) water splitting under visible light irradiation. A gradient distribution of N dopants along the vertical direction of ZnO nanorods was realized. N doped ZnO NRAs displayed a markedly enhanced visible-light-driven PEC photocurrent density of ~160 μA/cm2 at 1.1 V vs. saturated calomel electrode (SCE), which was about 2 orders of magnitude higher than pristine ZnO NRAs. The gradiently distributed N dopants not only extended the optical absorption edges to visible light region, but also introduced terraced band structure. As a consequence, N gradient-doped ZnO NRAs can not only utilize the visible light irradiation but also efficiently drive photo-induced electron and hole transfer via the terraced band structure. The superior potential of ion implantation technique for creating gradient dopants distribution in host semiconductors will provide novel insights into doped photoelectrode materials for solar water splitting.

which is composed of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). [1] Among them, OER displays a high thermodynamic voltage (1.23 V), because it needs more energy to overcome the sluggish kinetics of the four-electron reaction in comparison with the simple HER system (two-electron reaction). [2] Moreover, these two halfreactions typically undergo the different determining steps and chemisorption of the water-splitting intermediates, which often require different electrolytes to support them. [3] In addition, most catalysts can only be used for HER or OER, and employing diverse catalysts for an integrated electrolyzer requires sophisticated processes, resulting in increased costs. [4] Thus, it is indispensable to construct efficient bifunctional electrocatalysts and realize both efficient OER and HER. Initially, the precious metal catalysts were applied for water splitting, such as RuO 2 , IrO 2 for OER, and Pt/C for HER, but the scarcity, high cost, and poor stability hindered their promotion in industry application. [5] Ni metal is cheap, plentiful, and optimally positioned on the Volcano Plot, which means the moderate adsorption/desorption ability to the intermediate species, can be used to catalyze OER and HER simultaneously, usually owing superior performance to the noble metal catalysts. [6] Moreover, urea oxidation reaction (UOR, CO(NH 2 ) 2 + 6OH − → N 2 + CO 2 + 5H 2 O +6e − ) exhibits an intrinsic lower thermodynamic potential of 0.37 V, which can replace the OER as the anodic for electrolyzer to realize energy-saving H 2 production and urea wastewater treatment simultaneously. [7] In addition, UOR is the dominating reaction of direct urea fuel cells. [7b,8] Similar to OER, Ni metal and its derivatives have been reported to be the most promising in UOR catalysis. [9] Although Ni metal and its oxides or (oxy)hydroxides have been unremittingly designed for overall water and urea splitting, these catalysts suffer poor electrical conductivity, resulting in unsatisfactory catalytic performance and durability. Fortunately, Ni 3 S 2 , a metal chalcogenide occurs naturally as the pyrite and mineral heazlewoodite, has intrinsic metallic behavior because of Ni−Ni bonds throughout its structure, which exhibits better electrical conduction and corrosion resistance than nickel oxides or (oxy)hydroxides. [10] Moreover, Exploring earth-abundant, highly effective, and stable electrocatalysts for overall water and urea electrolysis is urgent and essential for developing hydrogen energy technology. Herein, a simple self-derivation method is used to fabricate a Fe-doped Ni 3 S 2 electrode. The electrode exhibits an impressive trifunctional catalyst, with low overpotentials of 290, 198, and 254 mV at 100 mA cm −2 for the oxygen evolution reaction (OER), urea oxidation reaction (UOR), and hydrogen evolution reaction (HER). The durability is higher than 3500 h (146 days) at 100 mA cm −2 for the OER without obvious change. In situ Raman spectra reveal the incorporation of Fe inhibited S dissol...

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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.

New nanostructural composites consisting of Ag nanoparticles (NPs)-SiO2-ZnO films were fabricated by depositing ZnO films on silica substrates which had already been implanted by Ag ions at different energies and fluences. The photoluminescence (PL) emission of ZnO films from these nanostructural composites can be enhanced or quenched comparing to that of a ZnO film directly deposited on bare silica substrate. The enhancement of the band gap emission is ascribed to the local field enhancement induced by the resonant coupling between the excitons of ZnO and the surface plasmons (SPs) of Ag NPs, while the quenching is due to the electron transfer from ZnO to Ag NPs. Our results can be used to clarify the ambiguity in controlling the light emission enhancement and quenching of a semiconductor coupled with the SPs of metal NPs, which is very important for the design and applications of semiconductor and metal coupling to highly efficient optoelectronic devices, biosensor, etc.