[en] Highlights: • CoFeCu alloys grown on Ni foam were prepared by electrodeposition method. • The introduction of Cu determined the structure and morphology of CoFeCu alloys. • CoFeCu alloys exhibited excellent catalytic activity for oxygen evolution reaction. • The CoFeCu electrode catalyst displayed great potential in practical application. -- Abstract: Water splitting requires efficient electrocatalysts to decrease overpotential of half-reaction-oxygen evolution reaction (OER). Herein, we report a dendritic CoFeCu ternary alloy grown on nickel foam (NF) electrode prepared with electrodeposited method as electrocatalyst for OER. The as-prepared CoFeCu/NF electrode catalyst has lots of holes and cracks on dendrites. The introduction of Cu leads to the formation of dendritic morphology. In addition, CoFeCu/NF electrode has fast charge transfer rate and large electrochemical surface area. The optimized CoFeCu/NF shows excellent electrocatalytic activity for OER with an overpotential of 202 mV when reaching current density (j) of 10 mA cm⁻² in 1.0 M KOH. As a result, dendritic CoFeCu/NF is one of the most promising electrocatalysts for OER, which shows great potential in practical application.

[en] Transition metal element doping into semiconducting materials has been a promising method for the preparation of active photocatalysts for the efficient use of solar energy. In this study, we report the facile synthesis of Fe doped SrWO₄ nanoparticles by a solvothermal method for photocatalytic nitrogen reduction. The intrinsic bandgap of SrWO₄ is greatly narrowed by the Fe-dopant which not only extends the light absorption from UV to visible light range, but also reduces the charge recombination. The narrowed band structure still fulfils the thermodynamic requirements of nitrogen reduction reaction. At optimal doping concentration, Fe doped SrWO₄ shows much higher photocatalytic nitrogen fixation performance. The present study provides a route toward the development of active photocatalysts for nitrogen fixation. (paper)

[en] Highlights: • Propose aday-ahead complementary operation model of wind, photovoltaic and hydropower plants . • Develop areal-time load allocation model to deal with the forecast uncertainty. • Evaluate the benefit and risk of the complementary operationsystem. The complementary operation of wind, photovoltaic and hydropower systems has the potential to increase the integration of renewable energy sources into an existing grid. However, the high variability and forecast uncertainty of wind and photovoltaic power may pose potential risks to the grid and cascade reservoirs. In this study, the benefit and risk of the complementary operation of the wind-photovoltaic-hydropower hybrid system are evaluated. First, an optimal day-ahead complementary operation model is proposed to guide the daily operation of the hybrid system. Then, an optimal real-time load allocation model is developed to deal with power generation derivation resulting from the uncertainty of wind and photovoltaic power forecasting. Finally, the benefit and risk of the complementary operation of the wind-photovoltaic-hydropower system are evaluated. A case study is performed with the wind-photovoltaic-hydropower system in the Yalong River basin of China. The results show that (1) the total power generation, the power generation profit, and the utilization efficiency of electricity transmission lines are significantly increased, but the profit of hydropower stations is sacrificed to compensate for wind and photovoltaic power generation; and (2) the negative effect of the variability of wind and photovoltaic power generation on the power grid can be alleviated; (3) reliable power supply can be achieved, and power loss occurs mainly in the flood season and the maximum load loss is acceptable; and (4) it may lead to an increase in release variation, especially in the dry season, and thus flood control gates and hydropower generating units need to be operated more flexibly.

[en] Highlights: • Bioinspired Fe doped SrMoO₄ photocatalyst is prepared by a facile solvothermal method. • The bandgap and light absorption of SrMoO₄ can be tuned by changing the doping concentration. • Fe doping can balance the defects and photocatalytic activity of nitrogen reduction. -- Abstract: Photocatalytic nitrogen reduction reaction (NRR) for the green synthesis of ammonia is a promising alternative way to the energy-intensive Haber-Bosch process. In this study, we report Fe doped SrMoO₄ by a solvothermal method for solar nitrogen reduction. It is found that Fe doping significantly changes the intrinsic bandgap of SrMoO₄ and extends the light absorption from UV light to visible light region. At optimal doping concentration, the Fe doped SrMoO₄ shows enhanced photocatalytic nitrogen reduction performance compared to the pristine SrMoO₄ in ultrapure water. The enhancement is ascribed to the optimized defect states, newly formed Fe–Mo active centers, and extended light absorption range. The characterization results show that Fe doping with optimal concentration not only prohibits the fast recombination of photoinduced charge carriers, but also promotes the interfacial charge transfer. The narrowed intrinsic bandgap enables the Fe doped SrMoO₄ to absorb more solar light while keeps the thermodynamic activity to nitrogen reduction with appropriate band energetics. The present study provides an effective strategy for the design of active nitrogen fixation photocatalysts.