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The mullite phase in porcelain is important to the porcelain strength; however, its formation from clay minerals usually requires high temperature. Here we found that the activation of kaolin by citric acid would lower the formation temperature of mullite phase to 935.1 °C, which is 67.5 °C lower than that for the raw kaolin. Needle-like mullite crystal, a desired crystal shape in kaolin, could be observed in activated kaolin at 1050 °C. The reduction of mullite formation temperature is due mainly to the surface change in kaolin. Upon citric acid activation, the pseudohexagonal platelets of kaolinite crystal are disintegrated to non-uniform flakes, and the specific surface area increases from 8.18 m 2 /g to 31.21 m 2 /g, both leading to improved activity of kaolin and increased sintering driving force. The results are of interest in producing high-strength porcelain at reduced sintering temperatures and consequent energy saving for sintering process. [ABSTRACT FROM AUTHOR]

• porous atomic layered 2H-MoS 2 was produced by one-step calcination treatment. • porous atomic layered 2H-MoS 2 exhibited an excellent catalytic activity for NRR. • porous structure activated the inert basal plane of MoS 2. • porous structure induced the generation of adjacent Mo atom pairs. • Adjacent Mo atom pairs were acted as active sites. MoS 2 has been proven to be an efficient NRR electrocatalyst, the activation of inert basal plane and rational utilization of basal plane have become the key to further increasing the activity. The defects of basal plane help to expose active sites, however, they cannot activate basal plane to promote NRR. Herein, based on the calculation results, we designed porous atomic layered 2H-MoS 2 (PAL-MoS 2) by one-step calcination treatment. The porosity of the basal plane effectively utilizes basal plane atoms while the presence of adjacent Mo atom pairs improves the NRR performance. A high Faradic efficiency of 44.36 % and a sizeable NH 3 yield of 3405.55 μg h−1 mg cat −1 (1.98 μg h−1 cm−2) at ‒0.1 V vs. reversible hydrogen electrode are obtained in 0.1 M HCl under ambient conditions, as far as we know, outperforming most of Mo-based NRR electrocatalysts reported before. Furthermore, this catalyst also exhibits high selectivity, electrochemical stability and good performance characterization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Found that NH 4 + eliminated the inhibitory effect of Cu2+ on sulfidization. • Found that NH 4 + worked with Cu2+ to further promote sulfidization. • Reveal the mechanism of action between NH 4 + and Cu2+. • Reveal the effects of Cu2+ and Cu(NH 3) 4 2+ on surface sulfidization. Ammonium sulfate [(NH 4) 2 SO 4 ] is an effective activator of malachite sulfidization flotation. In this work, we explored the effects of ammonium ion (NH 4 +) and copper ion (Cu2+) on malachite sulfidization flotation and investigated the underlying mechanism. Flotation experiments demonstrated that NH 4 + can not only eliminate the negative effects of Cu2+, but also work together with Cu2+ to further promote malachite sulfidization flotation in a certain concentration range. Zeta potential, SEM-EDS, and X-ray photoelectron spectroscopy analysis results indicated that the single Cu2+ weakened the oxidation of S (II) species on the malachite surface and reduced the formation of sulfides. In the presence of NH 4 +, Cu2+ did not inhibit the formation of sulfides on malachite surface but worked with NH 4 + to promote it. Aqueous speciation calculation and adsorption test revealed that NH 4 + and Cu2+ interacted to form Cu (II)–NH 3 complexes, which reacts with S (II) species to form a copper sulfide substance that is more easily adsorbed on the malachite surface than the copper sulfide colloid formed by the reaction between Cu2+ and S (II) species. This leads to the improvement of surface sulfidization. [ABSTRACT FROM AUTHOR]