High-entropy alloys for accessing hydrogen economy via sustainable production of fuels and direct application in fuel cells

Heavy consumption of fossil fuels has raised concerns over the climate change and energy security in the past decades.In this review,hydrogen economy,as a clean and sustainable energy system,is receiving great attention.The success of future hydrogen economy strongly depends on the storage of renewable energy in hydrogen and hydrogen-rich chemicals through electrolyzers and conversion back to electricity via fuel cells.Electrocatalysts are at the heart of these critical technologies and great efforts have been devoted to preparing highly efficient nanomaterials.High-entropy alloys(HEAs),with their unique structural characteristics and intrinsic properties,have evolved to be one of the most popular catalysts for energy-related applications,especially those associated with hydrogen economy.Herein,recent advances regarding HEAs-based hydrogen economy are comprehensively reviewed.Attention is paid to the discussion of emerged HEAs as a new class of materials in hydrogen energy cycle,carbon-based hydrogen energy cycle,and nitrogen-based hydrogen energy cycle,covering the sustainable electrochemical synthesis of hydrogen and hydrogen-rich fuels and their direct application in fuel cells.Based on this overview,the challenges and promising directions are proposed to guide the development of HEAs research,aiming to achieve significant progress for further accessing hydrogen economy.

Decarbonising energy: The developing international activity in hydrogen technologies and fuel cells

Hydrogen technologies and fuel cells offer an alternative and improved solution for a decarbonised energy future.Fuel cells are electrochemical converters;transforming hydrogen (or energy sources containing hydrogen) and oxygen directly into electricity.The hydrogen fuel cell,invented in 1839,permits the generation of electrical energy with high efficiency through a non-combustion,electrochemical process and,importantly,without the emission ofits point of use.Hitherto,despite numerous efforts to exploit the obvious attractions of hydrogen technologies and hydrogen fuel cells,various challenges have been encountered,some of which are reviewed here.Now,however,given the exigent need to urgently seek low-carbon paths for humankind’s energy future,numerous countries are advancing the deployment of hydrogen technologies and hydrogen fuel cells not only for transport,but also as a means of the storage of excess renewable energy from,for example,wind and solar farms.Furthermore,hydrogen is also being blended into the natural gas supplies used in domestic heating and targeted in the decarbonisation of critical,large-scale industrial processes such as steel making.We briefly review specific examples in countries such as Japan,South Korea and the People’s Republic of China,as well as selected examples from Europe and North America in the utilization of hydrogen technologies and hydrogen fuel cells.

Hydrogen Civilization Doctrine: Whether the Humankind Can Prevent Global Ecological Catastrophe?

Hydrogen Civilization (HyCi) doctrine is a novel world outlook, all-embracing vision of the sustainability of the human future: humanity can preclude world climate catastrophe and conserve the biosphere's ability to maintain the life of humanity by the only way, just by the sustainable movement along the vector "Hydrogen Energy → Hydrogen Economy → Hydrogen Civilization". HyCi doctrine is overcoming boundaries between different sciences, between peoples and nations. Hydrogen civilization is a public ideal ('superattractor') putting in the forefront Shakespeare's Hamlet question on a global scale: "To be or not to be the humankind: that is the question".

What would a US green hydrogen energy economy look like?

Detailed description is given for a hypothetical US hydrogen economy with solar and wind energy supplying virtually all current energy needs and with electrolytic hydrogen the energy carrier and storage medium.Fossil fuels provide nonfuel products(plastics,chemicals,cement and asphalt).Only current technologies are considered and hydrogen storage accommodates generation intermit-tency and variability,using pit storage of high-pressure vessels in open air,yielding daily storage round-trip energy installation costs of 722 and 538$/kWh for electric and thermal,respectively;and for power,2351 and 2240$/kW for electric and thermal,respectively.For long-duration storage,the costs are 94.1 and 23.8$/kWh and 937 and 845$/kW,respectively.Increased energy generation 20%over baseline accommodates low-season generation,obviates much required storage and ensures that reserves are topped off;96%of US 2022 total energy consumption is provided for.In the default scenario(demand energy portions:half photovoltaic,quarter on-shore wind and quarter offshore wind),the surface area for the farms(including offshore surface)requires~4.6%of the US 48-state land area.About 350 pit storage sites provide both daily and long-duration storage,with the latter accounting for complete loss of generation for 4 days over a quarter of the nation.Hydrogen pipelines and a renewed electric grid transmit and distribute energy.The installation cost of the public infrastructure is~$27.8 trillion for the default scenario.Alternative scenarios show significant in-frastructure and cost savings when batteries are used for transportation and/or utility storage,provided current insufficiencies can be overcome.Broadly,cost levels in money,surface and infrastructure are within existing levels already achieved in historical events and modern living.

Research progress in green synthesis of ammonia as hydrogen-storage carrier under‘hydrogen 2.0 economy’

Hydrogen energy is characterized by its environmental friendliness,high efficiency,lack of carbon emissions and wide range of applications.However,its transportation and storage are challenges that limit further development of the hydrogen-energy industry.Ammonia is a carbon-free hydrogen-rich carrier.The storage of hydrogen in ammonia has unique advantages of high energy density,easy storage and transportation,reliable safety,a mature industrial foundation and no tail-end carbon emissions.However,industrial ammonia synthesis still heavily relies on the Haber-Bosch process,which accounts for significant energy consumption and greenhouse gas emissions.Therefore,the development of green and sustainable ammonia-synthesis methods is extremely important and urgent.Recently,ammonia-synthesis technologies such as electrocatalysis,photocatalysis,photoelectrocatalysis and biocatalysis have successfully produced ammonia from nitrogen and water,resulting in lower costs.The nitrogen-reduction-reaction conditions of these methods are mild and can be carried out under ambient temperatures and atmospheric pressure with low energy consumptions.Meanwhile,these methods bypass the traditional hydrogen-production section and their routes are simpler.Therefore,these technologies can be used to flexibly integrate renewable energy,including intermittent renewable energy,to achieve distributed ammonia synthesis.These benefits contribute to both global energy and environmental sustainability goals.In this study,the mechanisms of ammonia synthesis under ambient conditions are reviewed and the technical difficulties of various catalysts for ammonia synthesis are summarized.Based on the optimization strategies reported for various catalysts,the high-performing catalysts reported for ammonia synthesis are reviewed and the developmental trend of this field has been forecasted.

Advancing green energy solution with the impetus of COVID-19 pandemic

The global energy system needs a revolutionary transition from today’s fossil fuel to a low carbon energy system by having deep carbonization in all energy demand sectors.Especially in the transport sector,fossil fuel-based vehicles contribute to a more massive amount of greenhouse gas emissions(GHG),mainly carbon dioxide(CO_(2))and particulate matter(PM2.5),affecting human health,society,and the climate system.Hydrogen and fuel cell technology is a promising low carbon transition pathway that supports GHG mitigation and achieves sustainable development.Although hydrogen and fuel cells are assuring,fuel cell vehicle expensiveness and the high cost of hydrogen production with the low carbon footprint are significant hindrances for its widespread deployment.Besides the situation above,the present corona virus(COVID-19)has devastated our global economy and ramps down the future of fossil fuel.It provides opportunities to rethink and reshape our energy system to a low carbon footprint.By utilizing the situation,governments and policymakers need to eliminate fossil fuel and invest in the hydrogen and fuel cell technologies deployment as future energy systems.This review article provides a technical overview of a low carbon energy system,production,and end-use service in a hydrogen economy perspective for developing a sustainable energy future.The techno-economic analysis of the different hydrogen production routines and fuel cell vehicles and their infrastructures are primarily focused.Finally,a long-term policy alignment was outlined to advance the hydrogen energy system for post-COVID-19 in the United Nation’s(UN)sustainable development goals framework.

A systemic review of hydrogen supply chain in energy transition

Targeting the net-zero emission(NZE)by 2050,the hydrogen industry is drastically developing in recent years.However,the technologies of hydrogen upstream production,midstream transportation and storage,and downstream utilization are facing obstacles.In this paper,the development of hydrogen industry from the production,transportation and storage,and sustainable economic development perspectives were reviewed.The current challenges and future outlooks were summarized consequently.In the upstream,blue hydrogen is dominating the current hydrogen supply,and an implementation of carbon capture and sequestration(CCS)can raise its cost by 30%.To achieve an economic feasibility,green hydrogen needs to reduce its cost by 75%to approximately 2$/kg at the large scale.The research progress in the midterm sector is still in a preliminary stage,where experimental and theoretical investigations need to be conducted in addressing the impact of embrittlement,contamination,and flammability so that they could provide a solid support for material selection and largescale feasibility studies.In the downstream utilization,blue hydrogen will be used in producing value-added chemicals in the short-term.Over the long-term,green hydrogen will dominate the market owing to its high energy intensity and zero carbon intensity which provides a promising option for energy storage.Technologies in the hydrogen industry require a comprehensive understanding of their economic and environmental benefits over the whole life cycle in supporting operators and policymakers.

Using machine learning to expound energy poverty in the global south:Understanding and predicting access to cooking with clean energy

Efforts towards achieving high access to cooking with clean energy have not been transformative due to a limited understanding of the clean-energy drivers and a lack of evidence-based clean-energy policy recommendations.This study addresses this gap by building a high-performing machine learning model to predict and understand the mechanisms driving energy poverty-specifically access to cooking with clean energy.In a first-of-a-kind,the estimated cost of US$14.5 trillion to enable universal access to cooking with clean energy encompasses all the intermediate inputs required to build self-sufficient ecosystems by creating value-addition sectors.Unlike pre-vious studies,the data-driven clean-cooking transition pathways provide foundations for shaping policy and building energy models that can transform the complex energy and cooking landscape.Developing these path-ways is necessary to increase people’s financial resilience to tackle energy poverty.The findings also show the absence of a linear relationship between electricity access and clean cooking-evidencing the need for a rapid paradigm shift to address energy poverty.A new fundamental approach that focuses on improving and sustaining the financial capacity of households through a systems approach is required so that they can afford electricity or fuels for cooking.