Recent Advances and Challenges of Hydrogen Production Technologies via Renewable Energy Sources

Currently, fossil fuels play a major role in meeting the world's energy demand. Fossil fuels, in contrast, threaten the planet's ecosystems and biological processes, contribute to global warming, and result in unfavorable climatic shifts. These energy sources are also finite and will eventually deplete. Thus, energy transition, which is the key from fossil fuels to renewable energy sources, is regarded as an essential course of action for decarbonizing the global economy and reducing the catastrophic and irreversible effects of climate change. Thereby using/consuming green hydrogen energy is a vital solution to meet the world's challenges. Subsequently, the pros and cons of several hydrogen generation methods, such as the conversion of fossil fuels, biomass, water electrolysis, microbial fermentation, and photocatalysis, are then compared and outlined in terms of their technologies, economies, consumption of energy, environmental aspects, and costs. Currently, the chemical industry uses green hydrogen (H 2 ) primarily to produce green emerging fuels methanol and ammonia (NH 3 ), which are regarded as alternate sources of energy. Finally, the current state of energy demands, recent developments in renewable energy sources, and the potential of hydrogen as a future fuel are outlined. Moreover, the discussion concludes with predicted opportunities and challenges.