The
decomposition of water into hydrogen and oxygen is an effective
method to generate new energy. How to develop highly efficient catalysts
with low cost for the hydrolysis of water is a huge challenge. Herein,
heterogeneous CDs/NiCo2S4/Ni3S2 nanorods were constructed on nickel foam (CDs/NiCo2S4/Ni3S2/NF) by Co ion exchange
on carbon dots (CDs) and sulfur codoped nickel foam (NF). The designed
CDs/NiCo2S4/Ni3S2/NF as
a self-standing electrocatalyst shows excellent electrocatalytic properties.
In the hydrogen evolution reaction process, the current density can
reach 10 mA cm–2 only with the overpotential of
0.127 V. During the oxygen evolution reaction process, overpotential
of 0.116 V is enough to achieve the same current density. Meanwhile,
the CDs/NiCo2S4/Ni3S2/NF
electrode can serve as both anode and cathode in alkaline electrolyte,
and overpotential of 1.50 V can drive the overall water splitting
with superior durability. Such excellent properties are mainly due
to (1) a large number of exposed active sites provided by carbon dots
modified transition metal chalcogenide (NiCo2S4 and Ni3S2), (2) the changed electronic structure
caused by the incorporation of carbon dots and Co ions and the synergistic
effect between NiCo2S4 and Ni3S2, (3) the accelerated electron transfer and mass transfer
processes owing to the hierarchical structure formed by 3D nickel
foam and one-dimensional CDs/NiCo2S4/Ni3S2/NF nanorods. This study can facilitate with
the production of efficient and non-noble metal catalysts for overall
water splitting.
A polyacrylonitrile‐based carbon fiber brush (PAN‐CFB) cathode was firstly used to decolorize and degrade methylene blue (MB) in Na2SO4 solution via electro‐Fenton reaction between H2O2 from oxygen reduction and ferrous ions (Fe2+) externally added. The optimal current value for H2O2 production was 300 mA, with a maximum H2O2 concentration of 185 mg L−1 and current efficiency of 68% after 60 min, indicating that PAN‐based CF is a promising electrode material for 2 e− oxygen reduction reaction. Additionally, the effect of different parameters, such as the initial pH of the dye solution, Fe2+ and initial dye concentration on the decolorization efficiency, and COD removal was thoroughly investigated in simulated wastewater containing MB. The results showed that the electro‐Fenton system using the PAN‐CFB cathode had a wide applicable pH range 3.00–7.00, and the optimal Fe2+ concentration was 0.3 mmol L−1. Moreover, under the conditions of 300 mA current, pH 3.00, and 0.3 mmol L−1 Fe2+, a nearly 100% color removal after 30 min, 95.9% chemical oxygen demand (COD) removal and the low electrochemical energy consumption of 11.6 kWh kg−1 COD after 60 min for 100 mg L−1 MB solution were obtained.
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