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1. Quantifying Soil Phosphorus Dynamics: A Data Assimilation Approach

   https://doi.org/10.1029/2018JG004903  

   Hou, Enqing; Lu, Xingjie; Jiang, Lifen; Wen, Dazhi; Luo, Yiqi (July 2019, Journal of Geophysical Research: Biogeosciences)

   Abstract The dynamics of soil phosphorus (P) control its bioavailability. Yet it remains a challenge to quantify soil P dynamics. Here we developed a soil P dynamics (SPD) model. We then assimilated eight data sets of 426‐day changes in Hedley P fractions into the SPD model, to quantify the dynamics of six major P pools in eight soil samples that are representative of a wide type of soils. The performance of our SPD model was better for labile P, secondary mineral P, and occluded P than for nonoccluded organic P (Po) and primary mineral P. All parameters describing soil P dynamics were approximately constrained by the data sets. The average turnover rates were labile P 0.040 g g⁻¹day⁻¹, nonoccluded Po 0.051 g g⁻¹day⁻¹, secondary mineral P 0.023 g g⁻¹day⁻¹, primary mineral P 0.00088 g g⁻¹day⁻¹, occluded Po 0.0066 g g⁻¹day⁻¹, and occluded inorganic P 0.0065 g g⁻¹day⁻¹, in the greenhouse environment studied. Labile P was transferred on average more to nonoccluded Po (transfer coefficient of 0.42) and secondary mineral P (0.38) than to plants (0.20). Soil pH and organic C concentration were the key soil properties regulating the competition for P between plants and soil secondary minerals. The turnover rate of labile P was positively correlated with that of nonoccluded Po and secondary mineral P. The pool size of labile P was most sensitive to its turnover rate. Overall, we suggest data assimilation can contribute significantly to an improved understanding of soil P dynamics. 

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2. A High‐Performance Symmetric Supercapacitor from Porous Activated Carbon under Compression

   https://doi.org/10.1002/ente.202100068  

   Sun, Wei; Zhang, Yulin; Yang, Fuqian (April 2021, Energy Technology)

   The realization of biomass‐derived supercapacitors of high performance is of practical importance for the manufacturing of supercapacitors from green and renewable sources. Herein, the feasibility of constructing high‐performance supercapacitors from potato‐derived activated carbon (AC) is demonstrated. The potato‐derived AC is produced from potato mash through hydrothermal treatment and high‐temperature activation with KOH as agent. The supercapacitors with aqueous electrolyte of 6 mKOH and a mass loading of 5 mg per electrode achieve a specific gravimetric capacitance of 333.7 F g⁻¹per electrode and a specific energy of 11.75 W h g⁻¹at a specific power of 197.6 W kg⁻¹at a current density of 0.4 A g⁻¹under a nominal compressive stress of 7.96 MPa. The supercapacitors with a mass loading of 10 mg per electrode achieve the maximum specific gravimetric capacitance of 340.6 F g⁻¹and a specific energy of 11.75 W h g⁻¹at a specific power of 194.2 W kg⁻¹at a current density of 0.4 A g⁻¹under a nominal compressive stress of 7.96 MPa. Increasing the compaction of electrode materials under compressive stress has the potential to increase the electrochemical performance of supercapacitors. 

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3. Oxalate content of vegetation and termite frass in western South Africa

   https://doi.org/10.1002/ecs2.70265  

   Nel, T.; Clarke, C_E; Francis, M_L; Babenko, D.; Breecker, D.; Cowan, D_A; Gallagher, T.; McAuliffe, J_R; Trindade, M. (May 2025, Ecosphere)

   Abstract Oxalate salts in organic matter are potential substrates for the oxalate‐carbonate pathway, which can sequester carbon in drylands. We compared calcium oxalate (CaOx) and water‐soluble oxalate (SOx) concentrations of samples of vegetation and termite excrement (frass) collected from termite mounds in sites across a regional rainfall gradient in western South Africa. We developed mid‐infrared (MIR) spectroscopic models to quantify oxalate components in vegetation extracts (n = 30) and frass samples (n = 39). The MIR spectroscopic method was more efficient than chemical analytical techniques of oxalate measurement. The median CaOx concentration of plants (0.311 mmol g⁻¹) was four times greater than frass (0.081 mmol g⁻¹), which may be explained by degradation of oxalates by microorganisms or selective harvesting of low‐oxalate vegetation by termites. The mean CaOx content of frass from sites in mesic regions (0.042 mmol g⁻¹) was lower relative to frass from sites in more arid regions (0.156 mmol g⁻¹), and lower in termite mounds (0.048 mmol g⁻¹) compared with off‐mound samples (0.131 mmol g⁻¹). Frass collected from sites with higher rainfall had a lower mean SOx content (0.006 mmol g⁻¹, respectively) compared with frass from sites with lower rainfall (0.013 mmol g⁻¹, respectively). This may be attributed to faster degradation of CaOx in soils with greater moisture content. Estimated annual inputs of carbon (17.6 kg mound⁻¹) and calcium (2.55 kg mound⁻¹, 20% of which occurs as CaOx) due to termite frass deposition may be instrumental in the formation of calcite via the oxalate‐carbonate pathway in soils of earthen mounds occupied by termites. This work is relevant to modeling carbon storage in drylands where termites are significant consumers of vegetation. 

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4. Molybdenum Carbide Electrocatalyst In Situ Embedded in Porous Nitrogen‐Rich Carbon Nanotubes Promotes Rapid Kinetics in Sodium‐Metal–Sulfur Batteries

   https://doi.org/10.1002/adma.202106572  

   Hao, Hongchang; Wang, Yixian; Katyal, Naman; Yang, Guang; Dong, Hui; Liu, Pengcheng; Hwang, Sooyeon; Mantha, Jagannath; Henkelman, Graeme; Xu, Yixin; et al (May 2022, Advanced Materials)

   Abstract This is the first report of molybdenum carbide‐based electrocatalyst for sulfur‐based sodium‐metal batteries. MoC/Mo₂C is in situ grown on nitrogen‐doped carbon nanotubes in parallel with formation of extensive nanoporosity. Sulfur impregnation (50 wt% S) results in unique triphasic architecture termed molybdenum carbide–porous carbon nanotubes host (MoC/Mo₂C@PCNT–S). Quasi‐solid‐state phase transformation to Na₂S is promoted in carbonate electrolyte, with in situ time‐resolved Raman, X‐ray photoelectron spectroscopy, and optical analyses demonstrating minimal soluble polysulfides. MoC/Mo₂C@PCNT–S cathodes deliver among the most promising rate performance characteristics in the literature, achieving 987 mAh g⁻¹at 1 A g⁻¹, 818 mAh g⁻¹at 3 A g⁻¹, and 621 mAh g⁻¹at 5 A g⁻¹. The cells deliver superior cycling stability, retaining 650 mAh g⁻¹after 1000 cycles at 1.5 A g⁻¹, corresponding to 0.028% capacity decay per cycle. High mass loading cathodes (64 wt% S, 12.7 mg cm⁻²) also show cycling stability. Density functional theory demonstrates that formation energy of Na₂S_x(1 ≤x ≤ 4) on surface of MoC/Mo₂C is significantly lowered compared to analogous redox in liquid. Strong binding of Na₂S_x(1 ≤x ≤ 4) on MoC/Mo₂C surfaces results from charge transfer between the sulfur and Mo sites on carbides’ surface. 

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5. Cobalt doping of tin disulfide/reduced graphene oxide nanocomposites for enhanced pseudocapacitive sodium-ion storage

   https://doi.org/10.1038/s42004-018-0086-z  

   Jia, Hao; Chen, Chen; Oladele, Olabode; Tang, Yongan; Li, Guoqing; Zhang, Xiangwu; Yan, Fei (November 2018, Communications Chemistry)

   Abstract Rechargeable sodium-ion batteries are receiving intense interest as a promising alternative to lithium-ion batteries, however, the absence of high-performance anode materials limits their further commercialization. Here we prepare cobalt-doped tin disulfide/reduced graphene oxide nanocomposites via a microwave-assisted hydrothermal approach. These nanocomposites maintain a capacity of 636.2 mAh g⁻¹after 120 cycles under a current density of 50 mA g⁻¹, and display a capacity of 328.3 mA h g⁻¹after 1500 cycles under a current density of 2 A g⁻¹. The quantitative capacitive analysis demonstrates that the electrochemical performance of the nanocomposite originates from the combined effects of cobalt and sulfur doping, resulting in the enhanced pseudocapacitive contribution (52.8 to 89.8% at 1 mV s⁻¹) of tin disulfide. This work provides insight into tuning the structure of layered transition metal dichalcogenides via heteroatom doping to develop high-performance anode materials for sodium-ion batteries. 

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