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TiO₂ supported catalysts have been widely studied for the selective catalytic reduction (SCR) of NO_x; however, comprehensive understanding of synergistic interactions in multi-component SCR catalysts is still lacking. For this work, transition metal elements (V, Cr, Mn, Fe, Co, Ni, Cu, La, and Ce) were loaded onto TiO₂ nanoarrays via ion-exchange using protonated titanate precursors. Amongst these catalysts, Mn-doped catalysts outperform the others with satisfactory NO conversion and N₂ selectivity. Cu co-doping into the Mn-based catalysts promotes their low-temperature activity by improving reducibility, enhancing surface Mn⁴⁺ species and chemisorbed labile oxygen, and elevating the adsorption capacity of NH₃ and NO_xmore » species. While Ce co-doping with Mn prohibits the surface adsorption and formation of NH₃ and NO_x derived species, it boosts the N₂ selectivity at high temperatures. By combining Cu and Ce as doping elements in the Mn-based catalysts, both the low-temperature activity and the high-temperature N₂ selectivity are enhanced, and the Langmuir–Hinshelwood reaction mechanism was proved to dominate in the trimetallic Cu–Ce–5Mn/TiO₂ catalysts due to the low energy barrier.« less

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Neutral aqueous zinc-ion batteries (ZIBs) have attracted considerable attention due to their safe and green features. As one typical cathode, birnessite MnO₂ (δ-MnO₂) suffers from low conductivity and structural instability, and its energy storage mechanism is still not well established yet. Herein, we developed a Zn-doped δ-MnO₂ material via a facile and effective microwave-assisted method for the cathode in aqueous ZIBs. By incorporating Zn to modify the microstructure and promote reaction kinetics, the Zn-doped δ-MnO₂ electrode demonstrates significantly enhanced electrochemical performance with an ultrahigh reversible capacity of 455 mA h g^–1 and excellent specific energy of 628 W h kg^–1.more » In addition, the successive insertion of H⁺ and Zn²⁺ and deep two-electron transfer routes are revealed systematically by ex situ experiments. In this study, the two-electron transfer route (Mn⁴⁺/Mn³⁺ and Mn³⁺/Mn²⁺) mechanism of Zn-doped δ-MnO₂ electrodes explains the exceedingly high capacity and opens new opportunities to develop high-energy aqueous ZIBs.« less

Efficient and long-term stable electrocatalysts for the hydrogen evolution reaction (HER) via water splitting are urgently desired to ease the energy crisis and develop the sustainability of human society. However, the HER performance of state-of-the-art Pt in non-acidic solutions is unsatisfactory due to the severely sluggish kinetics. In this work, DFT theoretical calculations reveal that the Ru/RuO₂ composites enable high HER activity to be pursued under non-acidic conditions because of the distinctive Ru and RuO₂ interface, which possess not only a strong capability to adsorb and dissociate water but also appropriate binding energies of H and OH. Therefore, we employmore » a simple strategy, including heating under an oxygen-poor environment and/or in situ electrochemical reduction, to partially reduce RuO₂. The formed Ru/RuO₂ interfaces demonstrate superior HER activities (e.g. η₁₀ = 17 mV, 35 mV dec^–1 in 1 M KOH) than Pt/C (e.g. η₁₀ = 27 mV, 58 mV dec^–1 in 1 M KOH) at both small (10–100 mA cm^–2) and large (1 A cm^–2) current densities in alkaline solution and even real seawater. Comprehensive experiments were conducted to investigate the structure-HER performance relationships. Moreover, benefiting from the bifunctional character of RuO2, a two-electrode system based on Ru/RuO₂ composites and RuO₂ exhibits the lowest cell voltage for water splitting in both 1 M KOH and 0.5 M H₂SO₄, respectively. A 300 h-stability test at 10 mA cm^–2 without an obvious decay demonstrates the industrial prospects of the Ru/RuO₂ composites to generate green energy.« less

Heterointerface engineering is a desirable way to rationally design efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER). Herein, urchin-like Co₉S₈@NiFe layered double hydroxide (Co₉S₈@NiFe LDH) heterostructured hollow spheres are assembled from Co₉S₈ hollow spheres as the core and porous NiFe LDH nanowires as the shell. The heterostructured hollow spheres show a small overpotential of 220 mV at a current density of 10 mA cm^-2, a low Tafel slope of 52.0 mV dec^-1, and robust stability, which is better than that of commercial IrO₂ and most reported non-precious electrocatalysts. Density functional theory (DFT) calculations show that the synergetic effectmore » at the interface could improve the electrical conductivity of Co₉S₈@NiFe LDH, induce electron transfer from NiFe LDH to Co₉S₈, and lower the energy barriers of intermediates for the OER, leading to enhanced electrocatalytic activity. Meanwhile, the urchin-like hollow structure with nanopores and super-hydrophilicity can provide desired structural stability, facilitate ion penetration and release bubbles, improving the accessibility of active sites and thereby boosting OER catalytic performance. This work provides a viable route to develop high performance electrocatalysts for the OER.« less