Roots are the interfaces between biochar particles and growing plants. Biochar application may alter root growth and traits and thereby affect plant performance. However, a comprehensive understanding of the effects of biochar on root traits is lacking. We conducted a meta-analysis with 2108 paired observations from 136 articles to evaluate the responses of root traits associated with 13 variables under biochar application. Overall, biochar application increased root biomass (+32%), root volume (+29%) and surface area (39%). The biochar-induced increases in root length (+52%) and number of root tips (+17%) were much larger than the increase in root diameter (+9.9%); this result suggests that biochar application benefits root morphological development to alleviate plant nutrient and water deficiency rather than to maximize biomass accumulation. Biochar application did not change root N concentration but significantly increased root P concentration (+22%), particularly when combined with N fertilization. Biochar application also affected root-associated microbes and significantly increased the number of root nodules (+25%). The responses of root traits to biochar application were generally greater in annual plants than in perennial plants and were affected by soil texture and pH values. Moreover, it appears that biochar production process (pyrolysis temperature and time) plays a more important role in regulating root growth than does biochar source. Together, findings obtained from this meta-analysis may have significant implications for the future sustainable development of biochar management to improve plant growth and functioning.

An unprecedented ukv topological framework, based on a rod-like cadium-carboxylate chain, exhibits high CO(2) sorption heat and sorption selectivities of CO(2) over N(2) and CH(4).

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Bauxite residue, a highly alkaline solid waste, is extremely hazardous to the surrounding environment and current research approaches have largely focused on the removal and separation of alkaline substances. Natural weathering processes may be a step forward in terms of their regeneration. In this study, natural evolution of basic alkalinity, electrical conductivity, exchangeable ions and acid neutralizing capacity of residue in the disposal areas is discussed. Minerals, exchangeable cations and alkaline anions were analyzed by X-ray powder diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and titration, respectively. Acid neutralizing capacity was carried out by batch neutralization experiments. Basic alkalinity, electrical conductivity, cation exchange capacity and exchangeable sodium percentage decreased with increasing disposal duration. Sodium was the predominant exchangeable cation in fresh residue but its concentration significantly decreased with increasing time from initial disposal. The acid neutralizing capacity of bauxite residue was investigated by incubation with hydrochloric acid. Acid neutralizing capacity curves changed with disposal duration and each revealed a characteristic buffering behavior that could be controlled by its alkaline components.

The combination of carbon materials and active metal materials can prepare newly fashioned and hierarchical porous materials. Meanwhile, the combined action of the two materials can effectively optimize the performance of electrode materials. The electrode material GO/Zn−Co−Ni layered double hydroxides (LDHs) (abbreviated as GO/ZCN) with a fluffy cotton-like structure is prepared via sacrificing the template GO/ZIF-8, showing a combination of carbon materials (GO) and triple hydroxides (Zn− Co−Ni LDHs). ZIF-8 easily solves the agglomeration of Zn−Co−Ni LDHs by discarding its own dodecahedral structure. The GO/ZCN exhibits a 843.0 C g −1 high specific capacitance, while the current density is 1 A g −1 . We can also utilize compressed GO/ZCN to acquire striking cycling stability (97.71% capacitance retention at 10 A g −1 at the end of 5000 charge−discharge circulations) which is improved greatly compared to uncompressed GO/ZCN. The supercapacitor device of GO/ZCN//activated carbon (AC) displays an excellent energy density (64.91 Wh kg −1 ), while the power density is 800 W kg −1 , and a good cycling stability performance (a specific capacitance retention of 98.96% is obtained after 10,000 charge−discharge cycles). Two fully charged and connected GO/ ZCN//AC ASC devices can have three different colored LEDs (light emitting diodes) sparkle at the same time and make a red LED glow for at least 50 min, showing a good practical application effect.

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To develop precious-metal-free bifunctional catalysts for overall water splitting, ultraeven Mo-doped CoP composites (Mo-CoP) have been fabricated by an in situ phosphorization protocol using CoMo-layered double hydroxide (CoMo-LDH) as the precursor. The ordered arrangement of cations in the CoMo-LDH could be easily phosphored and generate the ultraevenly dispersed Mo element within the CoP structure, resulting in the excellent bifunctional catalyst for overall water splitting. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activities of the composites present an increase first and then a decreasing tendency with increased Mo doping content. Among all the Mo-doped CoP materials, the composite with a Mo/Co mole ratio of 1/2.3 presents the highest HER activity and stability in acidic conditions. At the current density of −10 mA•cm −2 in 0.5 M H 2 SO 4 , the overpotential is only 116 mV. In addition, the composite also presents excellent HER and OER performance under alkaline conditions. The overpotential is 118 mV for HER and 317 mV for OER at 10 mA cm −2 in 1 M KOH. It requires a cell voltage of 1.7 V to achieve a current density of 10 mA•cm −2 and maintains a stable water-splitting current for at least 24 h, which is superior to most reported alkaline media. This simple and efficient synthetic approach could also be used for ultraeven doping between other transition metal ions.

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