Contemporary avenues of the Hydrogen industry: Opportunities and challenges in the eco-friendly approach.

Hydrogen (H) is a possible energy transporter and feedstock for energy decarbonization, transportation, and chemical sectors while reducing global warming's consequences. The predominant commercial method for producing H today is steam methane reforming (SMR). However, there is still room for development in process intensification, energy optimization, and environmental concerns related to CO emissions. Reactors using metallic membranes (MRs) can handle both problems. Compared to traditional reactors, MRs operates at substantially lower pressures and temperatures. As a result, capital and operational costs may be significantly cheaper than traditional reactors. Furthermore, metallic membranes (MMs), particularly Pd and its alloys, naturally permit only H permeability, enabling the production of a stream with a purity of up to 99.999%. This review describes several methods for H production based on the energy sources utilized. SRM with CO capture and storage (CCUS), pyrolysis of methane, and water electrolysis are all investigated as process technologies. A debate based on a color code was also created to classify the purity of H generation. Although producing H using fossil fuels is presently the least expensive method, green H generation has the potential to become an affordable alternative in the future. From 2030 onward, green H is anticipated to be less costly than blue hydrogen. Green H is more expensive than fossil-based H since it uses more energy. Blue H has several tempting qualities, but the CCUS technology is pricey, and blue H contains carbon. At this time, almost 80-95% of CO can be stored and captured by the CCUS technology. Nanomaterials are becoming more significant in solving problems with H generation and storage. Sustainable nanoparticles, such as photocatalysts and bio-derived particles, have been emphasized for H synthesis. New directions in H synthesis and nanomaterials for H storage have also been discussed. Further, an overview of the H value chain is provided at the end, emphasizing the financial implications and outlook for 2050, i.e., carbon-free H and zero-emission H.