Low Pt-Doped Crystalline/Amorphous Heterophase Pd12P3.2 Nanowires as Efficient Catalysts for Methanol Oxidation.

Pd-based catalysts are attractive anodic electrocatalysts for direct methanol fuel cells owing to their low cost and natural abundance. However, they suffer from sluggish reaction kinetic and insufficient electroactivity in methanol oxidation reaction (MOR). In this work, we developed a facile one-pot approach to fabricate low Pt-doped Pd12P3.2 nanowires with crystalline/amorphous heterophase (termed Pt-Pd12P3.2 NWs) for MOR. The unique crystalline/amorphous heterophase structures promote the catalytic activity by the plentiful active sites at the phase boundaries and/or interfaces and the synergistic effect between different phases. Moreover, the incorporation of trace Pt into Pd lattices modifies the electronic structure and improves the electron transfer ability. Therefore, the obtained Pt-Pd12P3.2 NWs display significantly enhanced electrocatalytic performance toward MOR with the mass activity of 2.35 A mgPd+Pt-1, which is 9.0, 2.9, and 2.0 times higher than those of the commercial Pd/C (0.26 A mgPd-1), Pd12P3.2 NWs (0.82 A mgPd-1), and commercial Pt/C (1.19 A mgPt-1). The high mass activity enables the Pt-Pd12P3.2 NWs to be the promising Pd-based catalysts for MOR.

Determination of the water-use patterns for two xerophyte shrubs by hydrogen isotope offset correction.

The stable hydrogen and oxygen isotope technique is typically used to explore plant water uptake; however, the accuracy of the technique has been challenged by hydrogen isotope offsets between plant xylem water and its potential source water. In this study, the soil hydrogen and oxygen isotope waterline was used to correct the hydrogen isotope offsets for Salix psammophila and Caragana korshinskii, two typical shrub species on the Chinese Loess Plateau. Five different types of isotopic data [(i) δ18O, (ii) δ2H, (iii) combination δ18O with δ2H, (iv) corrected δ2H and (v) combination δ18O with corrected δ2H] were separately used to determine the water-use patterns of the two shrubs. The δ2H offset values of S. psammophila and C. korshinskii did not show significant temporal variation among the sampling months (May, July and September) but showed notable differences between the two shrubs (-0.4 ± 0.5‰ in S. psammophila vs -4.3 ± 0.9‰ in C. korshinskii). The obtained water absorption proportion (WAP) of S. psammophila in the different soil layers (0-20, 20-60 and 60-200 cm) did not differ significantly among the five different input data types. However, compared with the input data types (iii) and (v), the data types (i), (ii) and (iv) overestimated the WAP of C. korshinskii in the 0-20 cm soil layer and underestimated that in the 60-200 cm layer. The data type (iii) overestimated the WAP of C. korshinskii in 0-20 cm soil layer (25.9 ± 0.8%) in July in comparison with the WAP calculated based on data type (v) (19.1 ± 1.1%). The combination of δ18O and corrected δ2H, i.e., data type (v), was identified as the best data type to determine the water use patterns of C. korshinskii due to the strong correlation between the calculated WAP and soil water content and soil sand content. In general, S. psammophila mainly used (57.9-62.1%) shallow soil water (0-60 cm), whereas C. korshinskii mainly absorbed (52.7-63.5%) deep soil water (60-200 cm). We confirm that the hydrogen isotope offsets can cause significant errors in determining plant water uptake of C. korshinskii, and provide valuable insights for accurately quantifying plant water uptake in the presence of hydrogen isotope offsets between xylem and source water. This study is significant for facilitating the application of the stable hydrogen and oxygen isotope technique worldwide, and for revealing the response mechanism of shrub key ecohydrological and physiological processes to the drought environment in similar climate regions.

Bismuth Incorporation in Palladium Hydride for the Electrocatalytic Ethanol Oxidation with Enhanced CO Tolerance.

Introducing nonmetal and oxophilic metal into palladium (Pd)-based catalysts is beneficial for boosting electrocatalysis, especially regarding the improvement of mass activity (MA) and CO tolerance. Herein, the stable bismuth-doped palladium hydride (Bi/PdH) networks have been successfully fabricated through a simple one-step method. The intercalation of interstitial H atoms expands the lattice of Pd, and the doping of oxophilic metal Bi restrains the adsorption of poisonous intermediates on the surface of Pd, thereby improving the activity and durability of the as-prepared catalysts in the ethanol oxidation reaction (EOR). The obtained Bi/PdH networks manifest a remarkable MA of 8.51 A·mgPd-1, which is 11.18 times higher than that of commercial Pd/C (0.76 A·mgPd-1). The CO-stripping analysis results indicate that Bi doping can significantly prohibit CO adsorption on the surface of the Bi/PdH networks. The density functional theory (DFT) calculations also reveal that Bi doping enhances the OH* adsorption on the catalyst surface and mitigates the interaction between Pd and CO* intermediates, providing deeper insights into the origin of the enhanced EOR activity and CO tolerance. This work describes an impactful path for producing high-performance and durable PdH-based nanocatalysts.

[Comprehensive evaluation of soil quality of different land use types on the northeastern margin of the Qinghai-Tibet Plateau, China]. / 青藏高原东北缘不同土地利用类型土壤质量综合评价.

Soil quality evaluation is an important prerequisite for the rational soil resource utilization. We collected soil samples from forest (n=9), grassland (n=18) and cropland (n=38) in Tianzhu County, Gansu Province, which is located on the northeastern edge of the Qinghai-Tibet Plateau. Soil quality was evaluated based on thirteen soil physical and chemical indicators, including soil bulk density, field capacity, and organic matter. A minimum data set (MDS) was constructed using principal component analysis and correlation analysis to establish a soil qua-lity evaluation index (SQI) system, which was used in the soil quality evaluation for the three land-use types. The results showed that total porosity, capillary porosity, field capacity, capillary water capacity, saturated water content, organic matter, total nitrogen and available potassium content were significantly higher in forest than those in grassland and cropland. The SQI system of forest was based on field capacity, organic matter, total nitrogen, available nitrogen, and available potassium, and the SQI ranged between 0.329 to 0.678, with a mean value of 0.481. Grassland SQI system was based on field capacity and available nitrogen, with the SQI ranging between 0.302 to 0.703 and a mean value of 0.469. Cropland SQI system was based on capillary water capacity, non-capillary porosity, available nitrogen, available phosphorus, and available potassium, and the SQI ranged from 0.337 to 0.616 with a mean value of 0.462. The most important barriers to soil quality improvement in forest, grassland, and cropland were available potassium, field capacity, and capillary water capacity, respectively. The MDS-based SQI enabled an accurate evaluation of soil quality across different land-use types in the study area, which was best in forest followed by grassland and cropland. The evaluation results would provide important reference for sustainable soil management in the local area.

Ternary PdCoP nanoparticles with nanopore structures: synergic boosting of electrocatalytic activity for ethanol oxidation.

PdCoP nanoparticles (PdCoP NPs) with nanopore structures were synthesized by a facile one-pot solvothermal approach. Due to their unique geometric structures and the electronic and synergistic effects among multiple components, the optimized PdCoP NPs (PdCoP-NPs-1) show superior mass activity (5.97 A mgPd-1) for the ethanol oxidation reaction under alkaline conditions.

[Effects of different re-vegetation patterns on soil organic carbon and total nitrogen in the wind-water erosion crisscross region, China].

This study was conducted to analyze the responses of soil organic carbon (SOC) and total nitrogen (TN) to three typical re-vegetation patterns, i.e., grassland, alfalfa land and peashrub land on the Loess Plateau of China, and also to assess the dynamics of SOC and TN with re-vegetation age. The results showed that all the three re-vegetation practices increased the concentrations of SOC and TN in the 0-10 cm soil layer, but their effects differed with re-vegetation age. Compared with adjacent croplands, the concentrations of SOC and TN in the 0-10 cm soil layer in grassland did not change within 10 years of succession, but increased after 20 years of succession. In alfalfa land, the concentrations of SOC and TN increased by 51.6%-82.9% and 43.4%-67.0% in the 0-10 cm soil layer, with the increasing rates of stocks of SOC and TN being 0.17-0.46 and 0.015-0.043 t · hm⁻² · a⁻¹, respectively. However, SOC and TN were not affected by re-vegetation age in alfalfa land. The increases of concentrations of SOC and TN remained high in the first 20 years after conversion of cropland to peashrub land, but decreased after 40 years of conversion. In conclusion, the conversion of croplands to peashrub or alfalfa land could be better in contributing to high stocks of SOC and TN than natural succession of grassland. However, their positive effects on the enrichment of SOC and TN may not be sustainable due to the scarcity of soil moisture and high water consumption of these two re-vegetation plants.

[Research advances in the calculating method of nitrogen use efficiency (NUE) in cultivated lands].

Nitrogen use efficiency (NUE) has received worldwide concern in the sphere of agronomic science and environmental science, and it is fundamentally important for evaluating N utilization status and optimizing N fertilization management in cultivated lands. In recent years, in consideration of low values and great variations of NUE in China' s cultivated lands, some scholars have discussed on the traditional concept and calculating method of NUE, and also have proposed some substituted NUE calculating methods. In this paper, we summarized some disadvantages of both conventional concept and calculating method of NUE, i.e. the subtraction method and the 15N labeling method. Furthermore, we particularly introduced several substituted NUE calculation methods and discussed research directions in the future. In summary, we strongly suggested the establishment of a comprehensive evaluation index system of N utilization in good accordance with the current agricultural production status in China, based on a correct understanding of the dialectical relationships among N application rate, crop yield, N utilization and N loss.

[Effects of different potassium fertilizer application periods on the yield and quality of Fuji apple].

In order to ascertain the effects of potassium fertilizer application periods on apple production, we conducted a field experiment and analyzed the differences in apple yield, fruit quality, potassium fertilizer use efficiency, and nutrient concentrations in leaves and fruits among treatments with differences in timing of potassium application. The results indicated that, compared with no potassium-applied treatment (CK), all potassium fertilizer application treatments significantly increased the apple yield by 4.3%-33.2%, meanwhile, it also obviously improved the fruit quality. In comparison with the application of 100% potassium fertilizer as a base, the application of 50% or 100% of potassium fertilizer at the fruit enlargement stage (the remaining 50% applied as a base or after flowering) significantly increased the apple yield by 20.5% - 27.7% and improved the fruit quality. Compared with the application 100% potassium fertilizer at the stage of fruit enlargement, the evenly split application as base flowering stage and at the fruit enlargement: stage not only contributed to a higher yield, better quality and higher potassium use efficiency, but also maintained a relatively stable potassium concentration level in leaves. However, the split potassium fertilizer application at the flowering and fruit enlargement stages resulted in the significant decrease in concentration of calcium in fruit, which would be negative to fruit quality. In conclusion, our research suggested that evenly split application of potassium fertilizer as a base and at the fruit enlargement stage was the suitable period for apple production in Fuji apple orchards in this region.

[Discussion on the calculation method of nitrogen use efficiency (NIUE) in long-term field experiments under wheat and maize rotation systems].

In recent years, some scholars from China have deeply discussed about the concept, connotation and calculating method of nitrogen use efficiency (NUE), and have raised questions and also put forward some improved methods for NUE calculation in cultivated lands. In this paper, we compared advantages and disadvantages of these improved NUE calculation methods by using the data from a 5-year positioning field experiment under a wheat-maize rotation system. The results indicated that it made mistakes when the traditional subtraction method was used to calculate NUE for wheat season and maize season separately, since the soil fertility level of experimental plots had differed significantly from each other after several seasons or years of different fertilization managements. Additionally, the calculated NUE increased markedly with the cropping season going, thus making it difficult to mirror the actual situation of N utilization in cultivated lands. For the wheat-maize rotation system, the cumulative NUE calculation method considered wheat season and maize season as a whole part, and skillfully avoided mistakes which could be caused by inhomogeneity of soil fertility levels between experimental plots. Moreover, the calculated NUE were comparably smaller, with smaller coefficient variations (CVs), in contrast with the traditional subtraction method. The NUE calculated by using the ratio method were bigger, with the smallest CVs, than that computed by using the cumulative calculation method. The soil N balance method took a thoughtful consideration about the budgets and losses of soil nutrients before and after crop growth, but obtained the largest values of NUE and CVs within these methods.

[Nitrate leaching characteristics of wheat-corn rotation farmland in Guanzhong area of Shaanxi].

By using in situ leaching device, a field experiment was conducted to study the effects of nitrogen fertilization rate and straw mulching on the nitrate leaching at 90 cm soil depth, nitrate accumulation in soil profile (0-100 cm), crop yield, and nitrogen balance of wheat-corn rotation farmland in Guanzhong area of Shaanxi. Six treatments were installed, i. e., no fertilization (N1, 0 kg x hm(-2) x a(-1)), conventional fertilization (N2, 471 kg x hm(-2) x a(-1)), recommended fertilization (N3, 330 kg x hm(-2) x a(-1)), reduced N application (N4, 165 kg x hm(-2) x a(-1)), increased N application (N5, 495 kg x hm(-2) x a(-1)), and recommended fertilization plus straw mulching (N3 + S). The nitrate leaching loss was increased with increasing N fertilization rate. Excessive N fertilization and straw mulching could easily cause nitrate leaching. In treatment N3 + S, the annual NO3(-) -N loss at 90 cm soil depth was the greatest (22.32 kg N x hm(-2)), and the NO3(-) -N loss from N fertilization was 16.44 kg N x hm(-2) x a(-1), being 158.9% higher than that in treatment N3. Nitrate mainly accumulated in 20-60 cm soil layer. When the N application rate was 330 kg N x hm(-2) x a(-1), straw mulching had less effect on the NO3(-) -N distribution in soil profile. No significant difference was observed in the crop yield among the treatments, but reduced N application (N4) tended to decrease the yield. Under our experimental condition, a fertilization rate of 150 kg N x hm(-2) x a(-1) for wheat and 180 kg N x hm(-2) x a(-1) for maize could ensure the crop production and reduce the soil nitrate leaching and accumulation.