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Among the transition metal dichalcogenides (TMD), tungsten disulfide (WS2) and molybdenum disulfide (MoS2) are promising sulfides for replacing noble metals in the hydrogen evolution reaction (HER) owing to their abundance and good catalytic activity. However, the catalytic activity is derived from the edge sites of WS2 and MoS2, while their basal planes are inert. We propose a novel process for N-doped TMD synthesis for advanced HER using N2 + Ar + H2S plasma. The high ionization energy of Ar gas enabled nitrogen species activation results in efficient N-doping of TMD (named In situ-MoS2 and In situ-WS2). In situ-MoS2 and WS2 were characterized by various techniques (Raman spectroscopy, XPS, HR-TEM, TOF–SIMS, and OES), confirming nanocrystalline and N-doping. The N-doped TMD were used as electrocatalysts for the HER, with overpotentials of 294 mV (In situ-MoS2) and 298 mV (In situ-WS2) at a current density of 10 mA cm−2, which are lower than those of pristine MoS2 and WS2, respectively. Density functional theory (DFT) calculations were conducted for the hydrogen Gibbs energy (∆GH) to investigate the effect of N doping on the HER activity. Mixed gas plasma proposes a facile and novel fabrication process for direct N doping on TMD as a suitable HER electrocatalyst. [ABSTRACT FROM AUTHOR]

Although climate change can be efficiently curbed by shifting to low-carbon (blue) hydrogen as an energy carrier to achieve carbon neutrality, current hydrogen production mainly proceeds via the gray pathway, i.e., generates large amounts of CO 2 as a byproduct. To address the need for cleaner hydrogen production, we herein propose novel CO 2 capture processes based on the integration of vacuum pressure swing adsorption into a gray hydrogen production process and perform retrofitting to a blue hydrogen production process for on-site hydrogen refueling stations. Techno-economic analysis reveals that the implementation of the proposed capture processes allows one to significantly reduce CO 2 emission while preserving thermal efficiency, and the economic feasibility of this implementation in different scenarios is determined by computing the levelized cost of hydrogen. As a result, blue hydrogen is shown to hold great promise for the realization of sustainable energy usage and the net-zero transition. [Display omitted] • Techno-economic analysis of blue vs. gray on-site H 2 production was performed. • Gray H 2 process was coupled with CO 2 capture via vacuum pressure swing adsorption. • CO 2 emission could be reduced while preserving process thermal efficiency. • Levelized cost of H 2 was compared as economic feasibility for different scenarios. [ABSTRACT FROM AUTHOR]

[Display omitted] • An induction heating-based reactor for ammonia decomposition is developed. • The reactor produced an ammonia conversion of >90.0 % at 600 °C and 7 bar. • Proposed process achieves a 150 Nm3/h carbon-free green hydrogen production. • Exergy analysis indicated an exergy efficiency of 54.21% for the overall process. • The levelized cost of hydrogen (LCOH) was calculated to be 6.98 USD/kgH 2. This study presents an induction heating-based reactor for ammonia decomposition and to achieve a 150 Nm3/h carbon-free green hydrogen production process. The developed metallic monolith reactor acts by increasing the reactor temperature through an electromagnetic induction method using renewable-based electricity. As a result, hydrogen is produced without the generation of air pollutants such as CO 2 , which are formed via the conventional production pathway. Furthermore, techno-economic analysis was conducted based on exergy and economic analysis to evaluate the feasibility of the developed process. Experimentally, the proposed reactor showed an ammonia conversion of 90.0 % at 600 ℃ and 7 barg. Exergy analysis indicated that the total unused exergy accounted for 45.79 % of the total exergy input, giving an exergy efficiency of 54.21 % for the overall process. Furthermore, the CAPEX and OPEX values are calculated as 1,599,567 USD and 644,719 USD/y, respectively; therefore, the levelized cost of hydrogen (LCOH) was calculated to be 6.98 USD/kgH 2. This study also demonstrated that the LCOH varies with the ammonia feed price and the process capacity, and so it would be expected to decrease from 6.98 to 5.33 USD/kgH 2 as the hydrogen production capacity is increased from 150 to 500 Nm3/h. Overall, our results confirm the feasibility of carbon-free green hydrogen production on on-site hydrogen refueling stations, and they will be expected to advance the development of an environmental hydrogen economy. [ABSTRACT FROM AUTHOR]

[Display omitted] • The induction-heating NH 3 -decomposition process was improved by adding new units. • The processes were evaluated via techno-economic and life-cycle assessments. • All proposed processes showed higher thermodynamic efficiency than the base case. • When using renewable energy, the proposed processes emit 2.45 to 3.21 kgCO 2 /kgH 2. • Adding a PEMFC is considered the most suitable improvement in all assessments. Ammonia (NH 3) is gaining attention as a hydrogen carrier due to its high H 2 storage capacity and ease of liquefaction at ambient temperatures. The conventional method of ammonia decomposition is thermal cracking through fossil fuel combustion, resulting in significant carbon dioxide (CO 2) emissions. Therefore, developing an eco-friendly and highly efficient ammonia decomposition process is important. This study proposed four high-efficiency processes without carbon emissions by improving the induction-heating-based ammonia decomposition process designed in a previous study. The four proposed processes were designed to utilize the H 2 discarded as off-gas of the PSA unit in the existing induction-heating-based ammonia decomposition process. The proposed processes incorporate various unit components, including a proton exchange membrane fuel cell (PEMFC), solid oxide fuel cell (SOFC), burner, and palladium (Pd) membrane. These units were integrated with the PSA outlet to achieve enhanced thermodynamic efficiency compared with the conventional process without carbon emissions. Energy, exergy, economic, and environmental analyses were conducted to assess the feasibility of each case. Thermodynamic analysis revealed that integrating the Pd membrane yields the highest thermal (78.29 %) and exergy (64.02 %) efficiencies. Integrating a PEMFC exhibits the lowest levelized cost of H 2 (6.93 USD/kg H 2). Finally, When the four proposed processes are operated with renewable energy, clean hydrogen can be produced at 2.45 to 3.21 kgCO 2 /kgH 2 emission levels. The enhanced processes presented in this study can serve as a blueprint for achieving carbon-free green H 2 production at on-site H 2 refueling stations. [ABSTRACT FROM AUTHOR]

In the transition of the global energy paradigm toward decarbonization, hydrogen is expected to play a crucial role as an energy vector. To enhance the sustainability of hydrogen as an energy source, it is important to reduce costs and carbon emissions in the hydrogen production. Among various hydrogen production technologies, the autothermal reforming (ATR)-based blue hydrogen production method can stand out as a promising option in terms of both economic and environmental considerations. However, there are several bottlenecks: (i) ATR requires an air separation unit that increases the cost burden, and (ii) conventional amine-based carbon capture method consumes a significant amount of energy. To address these bottlenecks, this study proposes a novel cryogenic carbon capture process for ATR-based blue hydrogen production. In the proposed process, air separation unit are utilized not only for oxygen production but also for carbon capture. The compressed air from the air separation unit provides cooling energy to the mixture gas, leading to solidification and separation of carbon dioxide. Despite imposing an additional burden on the air separation unit, it significantly reduces the energy and cost associated with carbon capture. Consequently, there exists a trade-off relationship between the increased load on the air separation unit and the decreased load in carbon capture. This trade-off was evaluated by comparing it with the conventional absorption-based carbon capture process in terms of energy and economic aspects. The proposed process exhibits a 36.4% reduction in total energy consumption, with a particularly approximately 49.5% decrease in the energy consumed for carbon capture (0.278 kW h/kg-CO 2). The economic performance indicates an 11% decrease in the levelized cost of hydrogen (1.62$/kg-H 2), and a 45.3% decrease in CO 2 avoidance cost (40.1$/kg-CO 2). The captured solid CO 2 can offer advantages during storage and transportation. Furthermore, the potential utilization of cooling energy of solid CO 2 from an end-user perspective is expected to contribute to the establishment of a new industrial value chain. [Display omitted] • A novel cryogenic CO 2 capture process is proposed for ATR hydrogen production. • The proposed process imposes a slight burden on the ASU but simplifies CO 2 capture. • In terms of overall H 2 production, an energy saving of 36.4% was achieved. • LCOH and CO 2 avoidance cost are 1.62$/kg-H 2 and 40$/kg-CO 2 , respectively. • The economic viability variations across diverse carbon scenarios were evaluated. [ABSTRACT FROM AUTHOR]