•Model quantifying hydrological effects of moss and fallen leaves was presented.•Moss and pine needles were considered as mulch rather than part of vadose zone.•CoreKarHydro performed well for ...simulating the soil water content curves.•CoreKarHydro is useful to understand effects of moss on soil evaporation.
Due to recent vegetation restoration projects in karst mountainous areas of China, the living moss and litter layer play important roles in controlling soil water dynamics in karst forests. However, the underlying mechanisms of the effects of moss and the litter layer on soil water dynamics are still controversial. To explore the underlying mechanisms, we employ the CoreKarHydro model, capturing soil water content dynamics driven by evapotranspiration and influenced by living moss and fallen leaves. This model integrates surface changes' impact on evapotranspiration, categorizing the domain into: no cover (S), moss (SM), pine needles (SP), and both (SMP). Model validation employs the MOCOM-UA method, using diverse metrics (RMSE, R2, ACC, ED, KGE and SA) against lysimeter data with 4 moss biomass levels and 3 pine needle biomass levels. The results indicated: 1) The CoreKarHydro model exhibited reliable performance in simulating the soil water content curves, with an RMSE ranging from 1.49% to 4.21% and an R2 value ranging from 0.60 to 0.77. 2) Among the factors that influenced evaporation processes, soil hydraulic properties emerged as the most sensitive parameters, whereas the properties of the moss and pine needles played a relatively lesser role. 3) The impact of moss cover on evaporation processes varied depending on the soil texture and the stage of evaporation. Moss cover reduced evaporation loss in 8 out of 12 soil textures (loamy sand, loam, silt, silt loam, sandy clay loam, silty clay loam, sandy clay, and silty clay). On the other hand, moss cover increased evaporation loss in 4 out of 12 soil textures (sand, sandy loam, clay loam, and clay). This study contributes to the understanding of the mechanisms of coupled soil-moss(litter)-hydrological processes in karst areas.
The number of catalytically reactive sites and their intrinsic electrocatalytic activity strongly affect the performance of electrocatalysts. Recently, there are growing concerns about layered double ...hydroxides (LDHs) for oxygen evolution reaction (OER). Exfoliating LDHs is an effective method to increase the reactive sites, however, a traditional liquid phase exfoliation method is usually very labor‐intensive and time‐consuming. On the other hand, proper heteroelement doping and edge engineering are helpful to tune the intrinsic activity of reactive sites. In this work, bulk CoFe LDHs are successfully exfoliated into ultrathin CoFe LDHs nanosheets by nitrogen plasma. Meanwhile, nitrogen doping and defects are introduced into exfoliated ultrathin CoFe LDHs nanosheets. The number of reactive sites can be increased efficiently by the formation of ultrathin CoFe LDHs nanosheets, the nitrogen dopant alters the surrounding electronic arrangement of reactive site facilitating the adsorption of OER intermediates, and the electrocatalytic activity of reactive sites can be further tuned efficiently by introducing defects which increase the number of dangling bonds neighboring reactive sites and decrease the coordination number of reactive sites. With these advantages, this electrocatalyst shows excellent OER activity with an ultralow overpotential of 233 mV at 10 mA cm−2.
Engineering the edge and corner active sites and realizing nitrogen incorporation in ultrathin N‐CoFe layered double hydroxides (LDHs) are implemented and synthesized simultaneously using N2 plasma to treat bulk CoFe LDHs nanosheets. With these unique features, the ultrathin N‐CoFe LDHs nanosheets as electrocatalyst show excellent oxygen evolution reaction properties.
Metal‐free electrocatalysts have been extensively developed to replace noble metal Pt and RuO2 catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in fuel cells or ...metal–air batteries. These electrocatalysts are usually deposited on a 3D conductive support (e.g., carbon paper or carbon cloth (CC)) to facilitate mass and electron transport. For practical applications, it is desirable to create in situ catalysts on the carbon fiber support to simplify the fabrication process for catalytic electrodes. In this study, the first example of in situ exfoliated, edge‐rich, oxygen‐functionalized graphene on the surface of carbon fibers using Ar plasma treatment is successfully prepared. Compared to pristine CC, the plasma‐etched carbon cloth (P‐CC) has a higher specific surface area and an increased number of active sites for OER and ORR. P‐CC also displays good intrinsic electron conductivity and excellent mass transport. Theoretical studies show that P‐CC has a low overpotential that is comparable to Pt‐based catalysts, as a result of both defects and oxygen doping. This study provides a simple and effective approach for producing highly active in situ catalysts on a carbon support for OER and ORR.
Edge‐rich, oxygen‐functionalized graphene can be in situ generated on the surface of carbon fibers by Ar‐plasma etching. Both oxygen doping and defects contribute significantly to enhanced electrocatalytic activity for the oxygen reduction reaction and oxygen evolution reaction.
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•The single crystal diamond (SCD) surface with ultra-low surface roughness and ultra-thin damage layer was obtained by CMP.•A novel CMP slurry was developed for the CMP of SCD ...consisting of SiO2, H2O2, FeSO4·7H2O, NTA and deionized water.•Under mixed effect of two oxidants, the post-polished surface quality of SCD was improved significantly.•The CMP mechanisms for a SCD were elucidated by XPS and IR measurements.
Single crystal diamond (SCD) has extremely high hardness and wear resistance. However, this hampers the development of surfaces with ultra-low surface roughness and ultra-thin damage layer. It is particularly challenging to achieve the chemical mechanical polishing (CMP) of SCD with a surface roughness less than 0.5 nm and a damage layer thickness <1 nm. In this study, the influence of the CMP slurries with different pH values and oxidants on the quality of polished SCD surface was investigated. The optimal slurry consisted of silica, ferrous sulfate, hydrogen peroxide, nitrilotriacetic acid, and deionized water achieved the lowest surface roughness of SCD. The average surface roughness Ra was 0.754 ± 0.062 nm over eight areas of 868 μm × 868 μm. The Ra value of 0.35 nm was obtained over a scanning area of 70 μm × 50 μm, while the thickness of the damage layer was 0.7 nm. The CMP mechanism was elucidated by X-ray photoelectron spectroscopy and infrared spectroscopy. Hydroxyl radicals and hydrogen ions were adsorbed on the surface, oxidation of the surface and generated C-H, C-O, and C = O groups, and they are eventually removed by silica abrasive, yielding an ultra-smooth SCD surface.
Designing highly active, earth-abundant and stable bifunctional electrocatalysts for both the oxygen (OER) and hydrogen (HER) evolution reactions is very crucial to overall water splitting. Herein, ...we developed nanoparticle-stacked porous Co
FeN
(NSP-Co
FeN
) nanowires as bifunctional electrocatalysts, exhibiting excellent OER and HER activity with a low overpotential of 222 mV at 20 mA cm
and 23 mV at 10 mA cm
, respectively, due to their unique structural advantages with grain boundaries, defects and dislocations. Moreover, the electrocatalysts as bifunctional electrodes show a high performance with 10 mA cm
at a cell voltage of 1.539 V.
•OpenKarHydro with multilayer soil water interactions was proposed.•OpenKarHydro reveals how climate and land use affect water budget and cause dry soil.•OpenKarHydro performs well in simulating the ...soil water content and runoff dynamics.•OpenKarHydro is a useful tool for land use optimization and controlling dry soil.
In water-limited areas, soil water content (SWC) is a critical factor for plant growth and ecosystem stability. To understand the long-term effects of three different land uses (Vigna radiata: VR, Stipa bungeana: SB, and Medicago sativa: MS) and two climate scenarios (representative concentration pathway 4.5 (RCP45) and nonclimate change (Non_CC)) on water budgets and the mechanisms of dried soil layer (DSL) formation, a new complete multilayered model, OpenKarHydro, was developed. The results showed that the model adequately captured the water budget for different land uses, with root mean square errors (RMSEs) of 0.058, 0.046, and 0.046 and coefficients of determination (R2) of 0.615, 0.605, and 0.582, respectively, for SWC dynamics. This model performance was also demonstrated by the verification of runoff. Sensitivity analysis indicated that the soil porosity (n) was the most sensitive parameter in all land uses. The DSL was primarily caused by higher evapotranspiration (VR: 83.16% vs. 82.48%, SB: 80.62% vs. 77.69%, and MS: 79.93% vs. 76.26%) and canopy interception (VR: 11.92% vs. 11.99%, SB: 17.56% vs. 23.15% and MS: 22.60% vs. 26.19%) in the Non_CC climate pattern than in the RCP45 climate pattern. Climate change has caused an increase in evapotranspiration and interception for all land uses, reducing bottom leakage. Rainfall is sufficient to meet the water demand in the VR plot regardless of climate change; however, the additional water consumption caused by climate warming cannot be offset by the increased rainfall for the SB and MS plots. Compared to Non_CC, RCP45 resulted in increases of 0%, 54.19%, and 57.62% in proportion with extreme drought and decreases of 4.70%, 38.74%, and 5.24% in proportion with no drought for the soil profiles of VR, SB, and MS, respectively. For MS, RCP45 (2026) caused the DSL to penetrate the soil profile (>400 cm) 4 years earlier than in the Non_CC (2030), which should take no more than 5 and 9 years, respectively. OpenKarHydro is a useful tool for optimal water resource management and ecological restoration in water-limited areas.
Nanoparticle-stacked porous Ni3FeN nanosheets were synthesized through a simple nitridation reaction of the corresponding LDHs. The nanosheet is composed of stacked nanoparticles with more active ...sites exposed for electrocatalytic reactions. Thus, it exhibited excellent oxygen evolution reaction performance having an extremely low overpotential of 223 mV at 10 mA/cm2 and hydrogen evolution reaction property with a very low overpotential of 45 mV at 10 mA/cm2. This electrocatalyst as bifunctional electrodes is used to overall water splitting in alkaline media, showing a high performance with 10 mA/cm2 at a cell voltage of 1.495 V.
•Ground cover effects on evaporation processes for karst mountainous lands were explored.•Pine needles had a much larger negative effect on evaporation rates than moss crusts.•Forest litter was very ...effective keeping temperature and humidity in karst mountain areas.•Ecohydrological role of ground cover controlling evaporation cannot be neglected for management.
The development of biocrusts and litter cover has been promoted by the vegetation restoration of karst mountainous lands in recent decades. However, the contribution of biocrust and litter to the karst terrestrial water cycle is still unclear. The interactive effects of moss crusts and pine needles on evaporation processes were explored by inserting microlysimeters (20 cm radius and 35 cm height) into the karst mountainous lands to collect undisturbed soils. Four moss crust biomass levels (0, 0.32, 0.64 and 0.96 kg m−2) and three pine needle biomass levels (0, 0.32 and 0.64 kg m−2) were used to estimate the influences of moss crusts and pine needles on evaporation losses and surface temperatures. In addition, the performances of two simplified evaporation concepts considering the interaction effects of moss crusts and pine needles were also assessed. The effect of pine needle cover on reducing evaporation rates was stronger than that of moss crusts. Moreover, the influences of moss crusts on the evaporation rate were obviously restricted by the higher biomass of pine needles, while the effects of pine needles on the evaporation rate were not highly affected by the moss crusts. Furthermore, thermal signatures showed that the pine needles had a much larger positive effect on the surface temperature (pr = 0.50) compared to the effect of the moss crusts (pr = 0.17). There was a significant relationship between the value of Ebare-soil/E0 and the mean soil water content SWCmean for bare soils. The predictive ability of the one-parameter concept (weighted average vegetation coefficient kc) was slightly better than that of the double-parameter concept (moss crust factor kMC and pine needle factor knp). The key ecohydrological role of ground cover in controlling evaporation cannot be neglected for karst mountainous land management and preventing rocky desertification.
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