Earth-abundant, low-cost electrocatalysts with outstanding catalytic activity in the electrochemical hydrogen evolution reaction (HER) are critical in realizing the hydrogen economy to lift our ...future welfare and civilization. Here we report that excellent HER activity has been achieved with three-dimensional core/shell Co/Co3O4 nanosheets composed of a metallic cobalt core and an amorphous cobalt oxide shell. A benchmark HER current density of 10 mA cm–2 has been achieved at an overpotential of ∼90 mV in 1 M KOH. The excellent activity is enabled with the unique metal/oxide core/shell structure, which allows high electrical conductivity in the core and high catalytic activity on the shell. This finding may open a door to the design and fabrication of earth-abundant, low-cost metal oxide electrocatalysts with satisfactory hydrogen evolution reaction activities.
Novel crystalline/amorphous core/shell Ni/NiO nanosheets have shown a high electrocatalytic activity in hydrogen evolution reaction (HER). In 1 M KOH, they display an HER current of 5 mA cm−2 at an ...overpotential of 110 mV with a good stability. It is proposed that their excellent HER performance is achieved through the synergistic effect between the Ni core and the amorphous NiO shell, where the Ni core can reduce the resistance and the amorphous NiO shell can accelerate both Volmer and Heyrovsky processes to drive HER at low overpotentials.
Excellent hydrogen evolution reaction activity has been achieved with novel crystalline/amorphous core/shell Ni/NiO nanosheets as electrocatalysts in alkaline conditions. Display omitted
•Novel crystalline/amorphous core/shell Ni/NiO nanosheets have been designed for HER.•The core/shell Ni/NiO nanosheets have a near-zero onset potential in alkaline condition.•An HER current of 5 mA cm−2 is achieved at a small overpotential of 110 mV.•The synergistic effect of Ni and amorphous NiO results in high catalytic activity.
Iron phosphide (FeP) has been recently demonstrated as a very attractive electrocatalyst for the hydrogen evolution reaction (HER). However, the understanding of its properties is far from ...satisfactory. Herein, we report the HER performance of FeP nanoparticles is enhanced after a stability test due to reduced surface-charge-transfer resistance in the HER process. The synthetic temperature and reactant ratio are important for surface-charge-transfer resistance, the electrochemically active surface area, and HER activity. Hydrogenation apparently improves the HER performance of FeP nanoparticles by reducing the surface-charge-transfer resistance, overpotential, and Tafel slope. Enhanced HER performance is observed after a stability test for both bare and hydrogenated FeP nanoparticles in the HER due to reduced surface-charge-transfer resistance. Thus, this study may enrich our knowledge and understanding to advance HER catalysis for electrochemical hydrogen generation.
Cold surge (CS) events are the most serious extreme cold events in winter in China, causing large economic losses and casualties. The occurrence of CS events has slightly increased since the 1990s. ...However, the possible future changes in these events remain unclear, and quantifying robust projected changes in CS events is important for developing adaptation and policy planning. Here, we project the occurrence of CS events and strong CS (SCS) events using the weighted multi-model ensemble (MME) of the Coupled Model Intercomparison Project 6 (CMIP6) through the application of the rank-based weighting (RBW) approach under three shared socioeconomic pathway (SSP126, SSP245, and SSP585) scenarios. The corresponding weights of each model were obtained depending on the comprehensive historical performance from three aspects: climatology, spatial variation, and interannual variability. The results show that the RBW approach can reduce the relative bias by approximately 50% compared to the unweighted MME. The occurrence of CS and SCS events shows a decreasing trend during 2015–2099 over northern China under the three SSP scenarios. There are also robust change projections during the long-term (2080–2099) and 2015–2099 periods under SSP245 and SSP585, especially in the NEC region, which exhibits a signal-to-noise ratio (SNR) that is >1. However, the occurrence of SCS events shows slight increases of 1.18% and 3.55% over northern China (notably western and eastern Northwest China) during the near-term (2020–2039) under SSP126 and SSP245, respectively. Obvious reductions in projected uncertainty are widespread throughout northern China after applying the RBW approach compared to the unweighted MME, which mainly depends on the scenario, region, and term variation. Then, a robust decreased frequency may contribute to projected changes in large-scale atmospheric circulation (a more positive AO and weaker SH and EAT) under SSP585. Our results emphasize that the weighted MME can be taken into account when projecting future extreme climate change in some areas to enhance reliability.
•Projected changes in cold surges are more credible using the rank-based weighting method compared to the unweighted MME.•A slight increase in strong cold surges during the near-term (2020–2039) under the SSP126 and SSP245 scenarios is expected.•The significant reduction in the projected uncertainty is >50% under the SSP585 scenario.
Piezoelectric energy harvesting is a hot topic in the field of new energy, and the key point is to design high power lead-free piezoelectric ceramic. In this work, a novel lead–free material system ...of (1–x)Ba(Zr0.1985Cu0.0015Ti0.8)O3-δ–x(Ba0.7Ca0.3)TiO3 (1–x)BZCT–xBCT was designed, and the energy harvesting characteristics were tailored through the composition-driven phase boundary evolution. The R–O–T phase boundary boosts the strong piezoelectric activity, obtaining an optimal energy harvesting performance. In the mode of the cantilever-type energy harvester, a high output power of 70μW and voltage of 8V were obtained at x=0.55 specimen with a low resonance frequency of 90Hz and acceleration of 10m/s2, which were further increased to 700μW and 25V when the acceleration increased to 50m/s2. The excellent low frequency characteristics show the potential applications of this material in piezoelectric generators harvesting environmental vibration energy.
After standardizing global land climate gridded data from the Climatic Research Unit TS (time-series) 3.1 dataset for the period 1901–2009, cluster analysis is used to objectively classify world ...climates into 14 climate types. These climate types establish a baseline classification map and the types are named according to Köppen–Geiger climate classifications. Although the cluster analysis and Köppen classification methods are very different, the distributions of climate types obtained by the two methods are similar. Moreover, the climate types we identify also coincide well with their corresponding vegetation types. Thus, cluster analysis can be used as an effective alternative to the Köppen classification method for classifying world climate types. The spatial and temporal changes in geographical distribution of global climate types were investigated in 25-year intervals, and Cohen’s kappa coefficient is used to detect agreement between the periods. Globally, although an obvious trend in increasing global temperature is found, distribution of climate types overall show no distinct changes over the periods. However, at the regional scale, spatial change in distribution of climate types is evident in South America and Africa. In South America, larger areas of the “fully humid equatorial rainforest” (Af) and “equatorial savannah with dry winter” (Aw) climate types have changed types. In Africa, changes mainly occurred in the Af, “equatorial savannah with dry summer” (As), Aw, “steppe climate” (BS), and “desert climate” (BW) climate types. Moreover, some climate types, including Af, “equatorial monsoon” (Am), BS, BW, and “tundra climate” (ET), were susceptible to temporal climate changes, especially in the period 1976–2009.
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Three-dimensional (3D) hierarchical hollow urchin-like NiO/NiCo2O4 heterostructures have been prepared via a facile one-pot hydrothermal method. The 3D urchin-like structure brings ...about high specific surface area of 40.2 m2 g−1. The NiO/NiCo2O4 heterostructures are composed of 59 wt% of NiO and 41 wt% of NiCo2O4 and enriched with NiO-NiCo2O4 phase boundaries. When used as catalysts for styrene oxidation reaction (SOR), the NiO/NiCo2O4 heterostructures present a markedly high selectivity of 90.8% to styrene oxide (SO) and a high SO yield of 81.4%. The high catalytic performance of the NiO/NiCo2O4 heterostructures can be attributed to the high specific surface area and the abundant NiO-NiCo2O4 phase boundaries, both of which contribute to the numerous active sites.
Coverage rate, a critical variable for gridded forest area, has been neglected by previous studies in estimating the annual gross primary production (GPP) of global forest ecosystems. In this study, ...we investigated to what extent the coverage rate could impact forest GPP estimates from 1982 to 2011. Here we show that the traditional calculation without considering the coverage rate globally overestimated the forest gross carbon dioxide uptake by approximately 8.7%, with a value of 5.12 ± 0.23 Pg C yr(-1), which is equivalent to 48% of the annual emissions from anthropogenic activities in 2012. Actually, the global annual GPP of forest ecosystems is approximately 53.71 ± 4.83 Pg C yr(-1) for the past 30 years by taking the coverage rate into account. Accordingly, we argue that forest annual GPP calculated by previous studies has been overestimated due to the exaggerated forest area, and therefore, coverage rate may be a required factor to further quantify the global carbon cycle.
The Three Rivers Source Region (TRSR) is a natural habitat for rare animals and a genetic treasure trove of plateau organisms. It is an important eco-safety barrier in China and even Asia, and a ...priority of China’s to promote ecological advancement. Precisely assessing the dynamics and mechanisms of alpine grassland ecosystem carbon budgets is beneficial for quantifying the response to climate change on a regional scale. The spatial distribution and dynamic changes in carbon fluxes in the TRSR from 1985 to 2018 were analyzed by the Theil–Sen + Mann–Kendall and ensemble empirical mode decomposition (EEMD) methods, and multiple linear regression was used to quantify the contribution of meteorological elements to the carbon flux trends. The results indicated that (1) the alpine grassland ecosystem was a weak carbon sink. The multiyear mean gross primary production (GPP) and net ecosystem production (NEP) in the TRSR were 147.86 and 11.27 g C/m2/yr, respectively. The distribution of carbon fluxes progressively decreased from east to west. (2) The carbon fluxes of the alpine grassland ecosystem were dominated by a monotonically increasing trend, with increasing rates of GPP and NEP of 1.31 and 0.40 g C/m2/yr, respectively. A total of 48.60% of the alpine grassland showed a significant increase in NEP, whereas only 0.21% showed a significant decrease during the research term. (3) The alpine meadow sequestered carbon better than the alpine steppe did and accounted for more than 60% of the regional carbon sink. (4) In a correlation analysis between NEP and temperature, precipitation and solar radiation, the positive correlation accounted for 89.67%, 90.51%, and 21.16% of the TRSR, respectively. Rising temperatures and increased precipitation were the main drivers contributing to the increase in NEP. Research on carbon budget variability and mechanisms can help guide preservation zoning initiatives in national parks.
This study demonstrates a facile and effective approach to prepare nitrogen/phosphorus co-doped nonporous carbon nanofibers (N/P-NPCNF5) through the electrospinning of the polyacrylonitrile and ...phosphoric acid precursor solutions and subsequent thermal treatment. X-ray photoelectron spectros-copy analyses show that the contents of phosphorus and pyrrol-like nitrogen in N/P-NPCNFs can be tuned by controlling the amount of phosphoric acid. The maximum specific capacitance of 224.9 Fg super(-1) is achieved at 0.5 A g super(-1) in I M H sub(2)SO sub(4). Furthermore, the specific capacitance could still remain 155.5 F g super(-1) at 30 A g super(-1) with a high capacitance retention ratio of 70%. It is worth noting that no capacitance loss is observed over 8000 charge/discharge cycles, clearly demonstrating a robust long-term stability. The excellent electrochemical performance can be attributed to the synergetic effect of nitrogen and phosphorus functionalities.
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