Rational Design of NiCo-borate/GO Heterojunction as a High-Performance Supercapacitor Electrode.

The bottleneck in the preparation of supercapacitors is how to develop high-energy and high-power-density devices by using appropriate materials. Herein, a novel NixCo3-x-B/GO heterostructure material was synthesized through a simple ultrasonic and precipitation method. The prepared NixCo3-x-B/GO heterostructure exhibits significant improvements in supercapacitor performance than NixCo3-x-B. The presence of GO effectively suppresses the excessive growth and accumulation of NixCo3-x-B; therefore, Ni2.7Co0.3-B/GO exhibits the best performance as an electrode material for supercapacitors: a high specific capacitance (Cm, 1789.72 F g-1@1 A g-1) and excellent rate performance. The asymmetric supercapacitor (ASC) device of Ni2.7Co0.3-B/GO//AC exhibits a Cm of 76.6 F g-1@1 A g-1, a large voltage window of 1.6 V, and a high energy density (ED) of 98.0 Wh kg-1. Furthermore, a flexible, all-solid-state supercapacitor assembled with Ni2.7Co0.3-B/GO as both the positive and negative electrodes demonstrates a Cm of 46.9 F g-1@1 A g-1. Even after multiple folding and bending at various angles, the device maintains excellent performance, showcasing remarkable stability. With a power density (PD) of 479.7 W kg-1, the device achieves a high ED of 60.0 Wh kg-1. This work provides valuable insights into the synergistic effects in electrochemical processes based on heterostructure materials.

Bidirectional Enhancement of Nitrogen Removal by Indigenous Synergetic Microalgal-Bacterial Consortia in Harsh Low-C/N Wastewater.

Conventional microalgal-bacterial consortia have limited capacity to treat low-C/N wastewater due to carbon limitation and single nitrogen (N) removal mode. In this work, indigenous synergetic microalgal-bacterial consortia with high N removal performance and bidirectional interaction were successful in treating rare earth tailing wastewaters with low-C/N. Ammonia removal reached 0.89 mg N L-1 h-1, 1.84-fold more efficient than a common microalgal-bacterial system. Metagenomics-based metabolic reconstruction revealed bidirectional microalgal-bacterial interactions. The presence of microalgae increased the abundance of bacterial N-related genes by 1.5- to 57-fold. Similarly, the presence of bacteria increased the abundance of microalgal N assimilation by 2.5- to 15.8-fold. Furthermore, nine bacterial species were isolated, and the bidirectional promotion of N removal by the microalgal-bacterial system was verified. The mechanism of microalgal N assimilation enhanced by indole-3-acetic acid was revealed. In addition, the bidirectional mode of the system ensured the scavenging of toxic byproducts from nitrate metabolism to maintain the stability of the system. Collectively, the bidirectional enhancement system of synergetic microalgae-bacteria was established as an effective N removal strategy to broaden the stable application of this system for the effective treatment of low C/N ratio wastewater.

Rational Design of FeCo-S/Ni2P/NF Heterojunction as a Robust Electrocatalyst for Water Splitting.

The rational design of nonnoble-metal-based catalysts with high electroactivity and long-term stability, featuring controllable active sites, remains a significant challenge for achieving effective water electrolysis. Herein, a heterogeneous catalyst with a FeCo-S and Ni2P heterostructure (denoted FeCo-S/Ni2P/NF) grown on nickel foam (NF) was synthesized by a solvothermal method and low-temperature phosphorization. The FeCo-S/Ni2P/NF catalyst shows excellent electrocatalytic performance and stability in alkaline solution. The FeCo-S/Ni2P/NF catalyst demonstrates low overpotentials (η) for both the hydrogen evolution reaction (HER) (49 mV@10 mA cm-2) and the oxygen evolution reaction (OER) (279 mV@100 mA cm-2). Assembling the FeCo-S/Ni2P/NF catalyst as both cathode and anode in an electrolytic cell for overall water splitting (OWS) needs an ultralow cell voltage of 1.57 V to attain a current density (CD) of 300 mA cm-2. Furthermore, it demonstrates excellent durability, significantly outperforming the commercial Pt/C∥IrO2 system. The results of experiments indicate that the heterostructure and synergistic effect of FeCo-S and Ni2P can significantly enhance conductivity, facilitate mass/ion transport and gas evolution, and expose more active sites, thereby improving the catalytic activity of the electrocatalyst for the OWS. This study provides a rational approach for the development of commercially promising dual-functional electrocatalysts.

Hollow Spherical Heterostructured FeCo-P Catalysts Derived from MOF-74 for Efficient Overall Water Splitting.

The design of catalysts with tunable active sites in heterogeneous interface structures is crucial for addressing challenges in the water-splitting process. Herein, a hollow spherical heterostructure FeCo-P is successfully prepared by hydrothermal and phosphorization methods. This hollow structure, along with the heterogeneous interface between Co2 P and FeP, not only facilitates the exposure of more active sites, but also increases the contact area between the catalyst and the electrolyte, as well as shortens the distance for mass/electron transfer. This enhancement promotes electron transfer to facilitate water decomposition. FeCo-P exhibits excellent hydrogen evolution (HER) and oxygen evolution (OER) performance when reaching @ 10 mA cm-2 in 1 mol L-1  KOH, with overpotentials of 131/240 mV for HER/OER. Furthermore, when FeCo-P is used as both the cathode and anode for overall water splitting (OWS), it only requires low voltages of 1.49, 1.55, and 1.57 V to achieve CDs of 10, 100, and 300 mA cm-2 , respectively. Density functional theory calculations indicate that constructing a Co2 P and FeP heterogeneous interface with good lattice matching can facilitate electron redistribution, thereby enhancing the electrocatalytic performance of OWS. This work opens up new possibilities for the rational design of efficient water electrolysis catalysts derived from MOFs.

Heterostructured MoO3 Anchored Defect-Rich NiFe-LDH/NF as a Robust Self-Supporting Electrocatalyst for Overall Water Splitting.

The rational design of inexpensive metal electrocatalysts with exciting catalytic activity for overall water splitting (OWS) remains a significant challenge. Heterostructures of NiFe layered double hydroxides (NiFe-LDHs) with abundant oxygen defects and tunable electronic properties have garnered considerable attention. Here, a self-supporting heterostructured catalyst (named MoO3/NiFe-NF) is synthesized via a hydrothermal method to grow NiFe-LDH with oxygen vacancies (OV) in situ on inexpensive nickel foam (NF). Subsequently, MoO3 is anchored and grown on the surface of NiFe-LDH by electrodeposition. The obtained catalysts achieved outstanding oxygen/hydrogen evolution reaction (OER/HER, 212 mV/85 mV@10 mA cm-2) performance in 1 m KOH. Additionally, when MoO3/NiFe-NF is utilized as the cathode and anode in OWS, a current density of 10 mA cm-2 can be obtained as an ultralow battery voltage of 1.43 V, a significantly lower value compared to the commercial electrolyzer incorporating Pt/C and IrO2 electrode materials. Finally, density functional theory (DFT) calculations and advanced spectroscopy technology are conducted to reveal the effects of heterojunctions and OV on the internal electronic structure of the electrical catalysts. Mainly, the present study provides a novel tactic for the rational design of remarkable, low-cost NiFe-LDH electrocatalysts with heterostructures for OWS.

Construction of a transition-metal sulfide heterojunction photocatalyst driven by a built-in electric field for efficient hydrogen evolution under visible light.

Photocatalytic H2 evolution is of prime importance in the energy crisis and in lessening environmental pollution. Adopting a single semiconductor as a photocatalyst remains a formidable challenge. However, the construction of an S-scheme heterojunction is a promising method for efficient water splitting. In this work, CdS nanoparticles were loaded onto NiS nanosheets to form CdS/NiS nanocomposites using hollow Ni(OH)2 as a precursor. The differences in the Fermi energy levels between the two components of CdS and NiS resulted in the formation of a built-in electric field in the nanocomposite. Density functional theory (DFT) calculations reveal that the S-scheme charge transfer driven by the built-in electric field can accelerate the effective separation of photogenerated carriers, which is conducive to efficient photocatalytic hydrogen evolution. The hydrogen evolution rate of the optimized photocatalyst is 39.68 mmol·g-1 h-1, which is 6.69 times that of CdS under visible light. This work provides a novel strategy to construct effective photocatalysts to relieve the environmental and energy crisis.

Enhanced Visible-Light-Induced Photocatalytic Activity in M(III)Salophen-Decorated TiO2 Nanoparticles for Heterogeneous Degradation of Organic Dyes.

In this work, the construction of two heterojunction photocatalysts by coordinative anchoring of M(salophen)Cl complexes (M = Fe(III) and Mn(III)) to rutile TiO2 through a silica-aminopyridine linker (SAPy) promotes the visible-light-assisted photodegradation of organic dyes. The degradation efficiency of both cationic rhodamine B (RhB) and anionic methyl orange (MO) dyes by Fe- and Mn-TiO2-based catalysts in the presence of H2O2 under sunlight and low-wattage visible bulbs (12-18 W) is investigated. Anionic MO is more degradable than cationic RhB, and the Mn catalyst shows more activity than its Fe counterpart. Action spectra demonstrate the maximum apparent quantum efficiency (AQY) at 400-450 nm, confirming the visible-light-driven photocatalytic reaction. The enhanced photocatalytic activity might be attributed to the improved charge transfer in the heterojunction photocatalysts evidenced by photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) analyses. A radical pathway for the photodegradation of dyes is postulated based on scavenging experiments and spectral data. This work provides new opportunities for constructing highly efficient catalysts for wastewater treatment.

Construction of ZIF-67-On-UiO-66 Catalysts as a Platform for Efficient Overall Water Splitting.

A well-organized construction of hybrid metal-organic frameworks (MOFs) with exquisite structures is vital due to their potential applications. Herein, a novel hybrid nanostructure of UiO-66-on-ZIF-67, denoted as MZU-CoxZry (x and y represent the mass ratios of ZIF-67 and UiO-66, respectively), was successfully prepared by a simple method and showed a highly efficient and stable bifunctionality of both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline medium. The MZU-Co2.5Zr1 shows remarkable OER performance with a low overpotential of 252 mV and an overpotential of 172 mV @ 10 mA/cm2 for HER in 1 mol/L KOH. With MZU-Co2.5Zr1 as the cathode and anode, the integrated water decomposition device has achieved low total potentials of 1.56 V @ 10 mA/cm2 and 1.59 V @ 30 mA/cm2, exhibiting its excellent performance of overall water splitting. Based on the experimental results, the mechanism of the superior electrocatalytic performance of MZU-CoxZry was discussed. This work supplies guidance for the rational design of non-precious composites for energy conversion.

Distribution of bacteriologically positive and bacteriologically negative pulmonary tuberculosis in Northwest China: spatiotemporal analysis.

Pulmonary tuberculosis (PTB) is a major health issue in Northwest China. Most previous studies on the spatiotemporal patterns of PTB considered all PTB cases as a whole; they did not distinguish notified bacteriologically positive PTB (BP-PTB) and notified bacteriologically negative PTB (BN-PTB). Thus, the spatiotemporal characteristics of notified BP-PTB and BN-PTB are still unclear. A retrospective county-level spatial epidemiological study (2011-2018) was conducted in Shaanxi, Northwest China. In total, 44,894 BP-PTB cases were notified, with an average annual incidence rate of 14.80 per 100,000 persons between 2011 and 2018. Global Moran's I values for notified BP-PTB ranged from 0.19 to 0.49 (P < 0.001). Anselin's local Moran's I analysis showed that the high-high (HH) cluster for notified BP-PTB incidence was mainly located in the southernmost region. The primary spatiotemporal cluster for notified BP-PTB (LLR = 612.52, RR = 1.77, P < 0.001) occurred in the central region of the Guanzhong Plain in 2011. In total, 116,447 BN-PTB cases were notified, with an average annual incidence rate of 38.38 per 100,000 persons between 2011 and 2018. Global Moran's I values for notified BN-PTB ranged from 0.39 to 0.69 (P < 0.001). The HH clusters of notified BN-PTB were mainly located in the north between 2011 and 2014 and in the south after 2015. The primary spatiotemporal cluster for notified BN-PTB (LLR = 1084.59, RR = 1.85, P < 0.001) occurred in the mountainous areas of the southernmost region from 2014 to 2017. Spatiotemporal clustering of BP-PTB and BN-PTB was detected in the poverty-stricken mountainous areas of Shaanxi, Northwest China. Our study provides evidence for intensifying PTB control activities in these geographical clusters.

Amorphous Yolk-Shelled ZIF-67@Co3(PO4)2 as Nonprecious Bifunctional Catalysts for Boosting Overall Water Splitting.

It is challenging to generate inexpensive and noble metal-free catalysts for efficient overall water splitting (OWS). To achieve this goal, suitable tuning of the structure and composition of electrocatalytic materials is a promising approach that has attracted much attention in recent years. Herein, novel hybrid amorphous ZIF-67@Co3(PO4)2 electrocatalysts with yolk-shell structures were prepared using a reflux method. It is demonstrated that yolk-shelled ZIF-67@Co3(PO4)2 is not only an active catalyst for the hydrogen evolution reaction (HER) but also an efficient catalyst for the oxygen evolution reaction (OER). The optimized composite electrode showed superior performance with low overpotentials of 73 and 334 mV @ 10 mA·cm-2 toward HER and OER, respectively, and a low potential of 1.62 V @ 10 mA·cm-2 and 1.66 V @ 30 mA·cm-2 in a practical OWS test under alkaline conditions. N-O bonds were formed to connect the two components of ZIF-67 and Co3(PO4)2 in the composite ZIF-67@Co3(PO4)2, which indicates that the two components are synergistic but not isolated, and this synergistic effect may be one of the important reasons to boost the oxygen and hydrogen evolution performances of the hybrid. Based on experimental data, the high electrocatalytic performance was inferred to be related to the unique structure of ZIF-67, tuning the ability of Co3(PO4)2 and synergism between ZIF-67 and Co3(PO4)2. The preparation strategy reported herein can be extended for the rational design and synthesis of cheap, active, and long-lasting bifunctional electrocatalysts for OWS and other renewable energy devices.