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The poor oxidation capacity of the Fe­(II)/S2O8 2– [Fe­(II)/PDS] system at pH > 3.0 has limited its wide application in water treatment. To unravel the underlying mechanism, this study systematically evaluated the possible influencing factors over the pH range of 1.0–8.0 and developed a mathematical model to quantify these effects. Results showed that ∼82% of the generated Fe­(IV) could be used for pollutant degradation at pH 1.0, whereas negligible Fe­(IV) contribution was observed at pH 7.5. This dramatic decline of Fe­(IV) contribution with increasing pH dominantly accounted for the pH-dependent performance of the Fe­(II)/PDS process. Unexpectedly, Fe­(II) could consume ∼80% of the generated SO4 •– non-productively under both acidic and near-neutral conditions, while the larger formation of Fe­(III) precipitates at high pH inhibited the SO4 •– contribution mildly. Moreover, the strong Fe­(II) scavenging effect was difficult to be compensated for by slowing down the Fe­(II) dosing rate. The competition of dissolved oxygen with PDS for Fe­(II) was insignificant at pH ≤ 7.5, where the second-order rate constants for reactions of Fe­(II) with oxygen were much lower than or comparable to that between Fe­(II) and PDS. These findings could advance our understanding of the chemistry and application of the Fe­(II)/PDS process.

The synergistic effect of high active surface/interface and optimized electronic structure of electrocatalysts is of great significance to improve the performance of hydrogen evolution reaction. Herein, a superhydrophilic core@shell heterostructure...

Metal sulfide electrocatalyst is developed as a cost-effective and promising candidate for hydrogen evolution reaction (HER). In this work, we report a novel Mo-doped Cu2S self-supported electrocatalyst grown in situ on three-dimensional copper foam via a facile sulfurization treatment method. Interestingly, Mo-Cu2S nanosheet structure increases the electrochemically active area, and the large fleecy multilayer flower structure assembled by small nanosheet facilitates the flow of electrolyte in and out. More broadly, the introduction of Mo can adjust the electronic structure, significantly increase the volmer step rate, and accelerate the reaction kinetics. As compared to the pure Cu2S self-supported electrocatalyst, the Mo-Cu2S/CF show much better alkaline HER performance with lower overpotential (18 mV at 10 mA cm−2, 322 mV at 100 mA cm−2) and long-term durability. Our work constructs a novel copper based in-situ metal sulfide electrocatalysts and provides a new idea to adjust the morphology and electronic structure by doping for promoting HER performance.

Exploring low-cost and highly active photocatalysts with noble-metal-free cocatalyst is of great significance for photocatalytic hydrogen evolution under simulate sunlight irradiation. In this work, a novel V doping Ni2P nanoparticles...