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Energy security and climate change are critical concerns in the present era. The booming of the vehicle population has worsened the environment and has caused severe air pollution problems, especially in urban areas. The utilization of hydrogen-enriched compressed natural gas in internal combustion engines shows abundant prospects for improved performance and reduced on-road emissions of greenhouse gases and air pollutants. This study aims to provide an insight to well-to-wheels environmental implications of the 20%HCNG fuel mixture in terms of total energy use, and greenhouse gas emissions per megajoules (MJ) of thermal energy output. The well-to-tank (WTT) impacts were evaluated using GREET 1 (2017). GREET 1 is a fuel cycle modeling tool developed by ‘Argonne national laboratory.’ GREET® is extensively used by researchers worldwide to analytically simulate energy use and emission output of various vehicle and fuel combinations. This study uses 12 prospective pathways of gaseous hydrogen production for analysis purposes. In the tank-to-wheels (TTW) phase, the 20%HCNG@EEV reduces the brake specific energy consumption (BSEC) by approximately 5%, and also decreases GHG emissions by 14% compared with 0%HCNG@EURO3. For simplicity, EURO5 is entitled as ‘EEV’ and has been excluded in most of the discussion, only highlighting ‘EEV,’ which abbreviates as ‘Enhanced Environmentally friendly Vehicles.’ For the entire well-to-wheels phase, this research work shows that all of the 20%HCNG@EEV pathways have lower total energy use and GHG emissions than 0%HCNG@EURO3 except the two pathways, such as grid electricity-to-hydrogen (without CO2 sequestration) and coal gasification-to-hydrogen (without CO2 sequestration). The WTW total energy and GHG emissions reduced by approximately 14% and 13%, respectively, with 20%HCNG@EEV based on the coke oven gas pathway compared with 0%HCNG@EURO3. It is essential to note that the use of cleaner feedstock for hydrogen, such as power-to-gas (P2G), biomass, coke oven gas (by-product), and natural gas shows tremendous prospects for realizing and practicing sustainable ‘hydrogen economy’ in China. Further technological advancement and reduction in total costs of HCNG utilization in powertrains will increase the number of HCNG vehicles decreasing the burden of air pollution, climate change, and energy crisis threats.

The effect of excess air ratio (λ) and ignition advance angle (θig) on the combustion and emission characteristics of hydrogen enriched compressed natural gas (HCNG) on a 6-cylinder compressed natural gas (CNG) engine has been experimental studied in an engine test bench, aiming at enriching the sophisticated calibration of HCNG fueled engine and increasing the prediction accuracy of the SVM method on automobile engines. Three different fuel blends were selected for the experiment: 0%, 20% and 40% volumetric hydrogen blend ratios. It is noted that combustion intensity varies with the excess air ratio and the ignition advance angle, so are the emissions. The optimal value of λ or θig has been explored in the specific engine condition. Results show that blending hydrogen can enhance and advance the combustion and stability of CNG engine, and it also has some benefic influence on the emissions such as reducing the CO and CH4. Meanwhile, a simulation research on forecasting the engine performance by using the support vector machine (SVM) method was conducted in detail. The torque, brake specific fuel consumption and NOx emission have been selected to characterize the power, economic and emissions of the engine with various HCNG fuels, respectively. It can be seen that the optimal model built by the SVM method can highly describe the relationship of the engine properties and condition parameters, since the value of the complex correlation coefficient is larger than 0.97. Secondly, the prediction performance of the optimal model for torque or BSFC is much better than the case of NOx. Besides, the optimal model built by the PSO optimization method has the best prediction accuracy, and the accuracy of the model obtained based on the training group with 20% hydrogen blend ratio is the best compared with those of others. The upshots in this article provide experimental support and theoretical basis for the adoption of HCNG fuel on internal combustion engines as well as the application of intelligent algorithmic in the engine calibration technology field.

Theoretical studies on the electrode materials in lithium-ion batteries provide information on the structural changes during the charging and discharging processes. In the present study, we tested the M06-L and N12 exchange-correlation functionals on some well-studied lithium-containing materials. These functionals, which have already shown good performance for a variety of databases, outperform the widely used PBE functional for reproducing the experimental structures and averaged intercalation potentials. It is especially noteworthy that the M06-L functional gives voltages as accurate as those provided by the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional, but with less computational cost.

The metal-organic framework Fe2(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate), often referred to as Fe-MOF-74, possesses many interesting properties such as a high selectivity in olefin/paraffin separations. This compound contains open-shell Fe(II) ions with open coordination sites which may have large single-ion magnetic anisotropies, as well as isotropic couplings between the nearest and next nearest neighbor magnetic sites. To complement a previous analysis of experimental data made by considering only isotropic couplings [Bloch et al. Science 2012, 335, 1606], the magnitude of the main magnetic interactions are here assessed with quantum chemical calculations performed on a finite size cluster. It is shown that the single-ion anisotropy is governed by same-spin spin-orbit interactions (i.e., weak crystal-field regime), and that this effect is not negligible compared to the nearest neighbor isotropic couplings. Additional magnetic data reveal a metamagnetic behavior at low temperature. This effect can be attributed to various microscopic interactions, and the most probable scenarios are discussed.