Construction of phase-separated Co/MnO synergistic catalysts and integration onto sponge for rapid removal of multiple contaminants.

Wastewater treatment recycling is critical to ensure safe water supply or to overcome water shortage. Herein, we developed metallic Co integration onto MnO nanorods (MON) resulting in a phase-separated synergetic catalyst by creating more Mn(III) via the Jahn-Teller effect and oxygen vacancies and improving the redox capability of Co nanoparticles mediated by a thin carbon layer. Additionally, the N-doped surface carbon network on MON contributes to polar sites, facilitating the enrichment of contaminants around reactive sites, thereby shortening the migration of reactive oxidative species (ROS) toward contaminants. The optimized MnO@Co/C-600 exhibits superior PMS activation efficiency for bisphenol A degradation (0.463 min-1), displaying nearly a 20-fold enhancement in the rate constant compared to Mn3O4/C-600. Subsequent experiments involving variable modulation and extension were conducted to further elucidate the multiple synergistic effects. The mechanism study further confirms the synergy of ˙SO4-, ˙OH, ˙O2-, and 1O2, along with additional electron transfer pathways. The intermediates generated during degradation pathways and their toxicity to aquatic organisms were identified. Notably, a monolith integrated catalyst was explored by anchoring MnO@Co/C-600 onto a tailored melamine sponge based on Ca ion triggered crosslink tactic for the photothermal degradation of bisphenol A, tetracycline and norfloxacin, endowed with easy recovery and good stability. Furthermore, we demonstrated that the total organic carbon removal of multiple contaminants surpassed that of sole contaminants.

Efficient oxygen evolution reaction from iron-molybdenum nitride/molybdenum oxide heterostructured composites.

Integrating various active sites into a multi-component system might significantly enhance the oxygen evolution reaction (OER) performance. Herein, the as-prepared iron-molybdenum nitride/molybdenum oxide (Fe-Mo5N6/MoO3-550) composite electrocatalyst under optimum conditions demonstrates excellent electrocatalytic performance toward OER and reaches current densities of 10 and 20 mA cm-2 at overpotentials of 201 and 216 mV, respectively. The OER performance of Fe-Mo5N6/MoO3-550 exceeds that of most previously reported electrocatalytic systems. The significant improvement in the OER performance is ascribed to a combination of mechanisms. The strong electronic interactions among the Fe, Mo5N6 and MoO3 species can accelerate the OER reaction kinetics, which contributes to the OER performance. This work provides new insights into the construction of efficient electrocatalytic materials with inexpensive metals.

Boosted hydrogen evolution reaction for a nitrogen-rich azo-bridged metallated porphyrin network.

The potential of porous organic polymers (POPs) toward electrocatalytic water splitting have attracted considerable scientific attention, due to their high specific surface areas, superlative porosity and diverse electronic structures; yet it remains challenging. Herein, we report a facile synthesized novel nitrogen-rich azo-bridged metallated porphyrin POP (CoTAPP-CoTNPP) for improving the hydrogen evolution reaction (HER) activity. The incorporation of the cobalt porphyrins and the azo groups endows CoTAPP-CoTNPP with effective charge transfer efficiency and large π-conjugated porous frameworks, thus enhancing the HER performance. Origins of the excellent HER performance of the material are evaluated using a series of structural and electrochemical measurements. Remarkably, CoTAPP-CoTNPP exhibits low overpotentials of 103 and 170 mV to reach 10 mA cm-2 in acidic and alkaline media, respectively, outperforming many previously reported HER electrocatalysts. These results demonstrate the enormous potential of the as-prepared azo-linked porphyrin POP for electrocatalytic water splitting.

Construction of a TiO2/BiOCl heterojunction for enhanced solar photocatalytic oxidation of nitric oxide.

TiO2/BiOCl heterojunction photocatalysts with different molar ratios (Ti : Bi) were synthesized by a simple solvothermal method. Various spectroscopic techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), nitrogen adsorption-desorption, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) were used to characterize the prepared photocatalysts. The photocatalytic activity of the catalysts was investigated by removing low concentrations of nitrogen oxides. The characterization results show that the TiO2/BiOCl composite photocatalyst exhibits superior visible light response performance than pure BiOCl and TiO2. The optimized TiO2/BiOCl heterojunction with a Ti : Bi molar ratio of 4 : 1 has the best photocatalytic performance. The removal rate of nitrogen oxides of the composite photocatalyst can reach 75%, which is 2.34 times higher than that of pure BiOCl. The observed photocatalytic degradation activity of nitrogen oxides outperforms current state-of-the-art functional photocatalysts. The TiO2/BiOCl composite photocatalyst has a larger specific surface area, stronger visible light absorption and higher charge separation efficiency compared to other control samples, which contribute to the enhanced photocatalytic activity. The experimental results indicate that the combination of TiO2 with BiOCl is a promising technique to design visible light-responsive photocatalysts.

Enhanced hydrogen storage kinetics of MgH2 by the synergistic effect of Mn3O4/ZrO2 nanoparticles.

As an ideal material for solid-state hydrogen storage, magnesium hydride (MgH2) has attracted enormous attention due to its cost-effectiveness, abundant resources, and outstanding reversibility. However, the high thermodynamics and poor kinetics of MgH2 still hinder its practical application. In this work, a simple stirring-hydrothermal method was used to successfully prepare bimetallic Mn3O4/ZrO2 nanoparticles, which were subsequently doped into MgH2 by mechanical ball milling to improve its hydrogen sorption performance. The MgH2 + 10 wt% Mn3O4/ZrO2 composite began discharging hydrogen at 219 °C, which was 111 °C lower compared to the as-synthesized MgH2. At 250 °C, the MgH2 + 10 wt% Mn3O4/ZrO2 composite released 6.4 wt% hydrogen within 10 min, whereas the as-synthesized MgH2 reluctantly released 1.4 wt% hydrogen even at 335 °C. Moreover, the dehydrogenated MgH2 + 10 wt% Mn3O4/ZrO2 sample started to charge hydrogen at room temperature. 6.0 wt% hydrogen was absorbed when heated to 250 °C under 3 MPa H2 pressure, and 4.1 wt% hydrogen was taken up within 30 min at 100 °C at the same hydrogen pressure. In addition, compared with the as-synthesized MgH2, the de/rehydrogenation activation energy values of the MgH2 + 10 wt% Mn3O4/ZrO2 composite were decreased to 64.52 ± 13.14 kJ mol-1 and 16.79 ± 4.57 kJ mol-1, respectively, which incredibly contributed to the enhanced hydrogen de/absorption properties of MgH2.

Strongly Coupled Nitrogen-Doped Mo2C@CoNi Alloy Hybrid Architecture toward Efficient Hydrogen Evolution Reaction.

Development of high-efficiency electrocatalysts for water splitting is a promising channel to produce clean hydrogen energy. Herein, we demonstrate that the combination of nitrogen-doped Mo2C and CoNi alloy to form a hybrid architecture is an effective way to produce hydrogen from electrochemical water splitting. Benefiting from a combination of mechanisms, the optimized N-Mo2C@CoNi-650 shows remarkable hydrogen evolution reaction (HER) activity with small overpotentials of 35, 123, and 220 mV to reach the current density of 10, 50, and 100 mA cm-2 in alkaline media, respectively, outperforming most previously reported HER electrocatalysts. The efficient electrocatalytic performance is ascribed to the highly exposed active sites, fast reaction kinetics, and improved charge-transfer steaming from the synergistic effect between each component. This work presents a new insight into designing and preparing highly efficient electrocatalysts toward the HER.

Enhanced optical limiting and hydrogen evolution of graphene oxide nanohybrids covalently functionalized by covalent organic polymer based on porphyrin.

Herein, we report a novel graphene oxide (GO) nanohybrid covalently functionalized by covalent organic polymer (COP) based on porphyrin (GO-TPPCOP), as the optical limiter and hydrogen evolution reaction (HER) electrocatalyst. The GO-TPPCOP nanohybrid exhibits markedly enhanced optical limiting and HER activity over that of TPP, GO and TPPCOP alone. More importantly, the optical limiting property and HER activity of GO-TPPCOP nanohybrid are comparable to the state-of-the-art activity of materials from some previous reports. The possible mechanisms of optical limiting and HER are explored by various means, including UV-Vis absorption, fluorescence, photocurrent, electrochemical impedance spectra and Raman spectroscopic techniques. It is demonstrated that the synergistic effect and charge transfer between GO and TPPCOP are important factors in determining its optical limiting and HER performances. These results demonstrate a new strategy to design and develop functional nanohybrids for efficient optical limiting and HER activity by the covalent linkage of GO with COPs.

Ti3+ doped V2O5/TiO2 catalyst for efficient selective catalytic reduction of NOx with NH3.

The effect of self-doping Ti3+ into V2O5/TiO2 catalysts on the activity of the catalysts was assessed by the selective catalytic reduction of NOX with NH3 (NH3-SCR). 0.2-V2O5/TiO2 (Al(acac)3:TBOT = 0.2%) catalyst had the highest catalytic activity at low-temperature range. The as-prepared catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD), surface area and pore structure. XPS and EPR were used to confirm the existence of Ti3+ and oxygen vacancy in the catalysts. The specific surface area, surface acidity, reducibility and valence state of the active components of the catalysts are significantly affected by the self-doping of Ti3+. This work would lead to a new strategic design of Ti3+ self-doped catalysts with fine structure and that can efficiently improve low-temperature SCR performance.