Overview: Fuel Cells, Hydrogen Energy, Science, Materials, Nanotechnology, Artificial Intelligence and State of the Art

Fuel Cells (FCs), typically hydrogen energy based, obtained from various sources, are important electricity producing technologies that could help provide the renewable, sustainable energy we need, with mostly water as by-product, whereas electrical power output could be sustained indefinitely. The FCs anode/electrolyte/cathode technology converts the fuel’s chemical energy into electricity with near-zero emissions, high efficiency, low maintenance, high energy density, no need to recharge, reusability of heat and long usage time. Pure hydrogen can be used as fuel whereas for oxidizing agent the ambient oxygen containing air can be used. Hydrogen (green, blue, grey …), versatile energy carrier, can be produced from thermochemical, electrochemical, biochemical technologies (electrolysis, steam reforming, photolysis, fermentation) using various types of feedstocks, stored (liquid, compressed, cryogenic, solid state) and transported (tanks, pipelines, trucks) in the challenging hydrogen technology. We overview the field of hydrogen energy and FCs indicating actual state of the art as well as future trends and perspectives. We summarize the fundamental science/technology of FCs, materials, operation temperature ranges, hydrogen oxidation reactions (HOR), oxygen reduction reactions (ORR), devices typically named after electrolytes used, i.e. solid oxide fuel cells (SOFC), alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), proton exchange membrane fuel cells (PEMFC) and molten carbonate fuel cell (MCFC). We also comment on other FCs including direct ethanol fuel cells (DEFC), direct formic acid fuel cells (DFACs), direct methanol fuel cells (MDFC), direct borohydride fuel cell (DBFC), direct carbon fuel cells (DCFC), direct glycerol fuel cells (DGFCs), biofuel cells (BFCs), glucose fuel cells (GFCs), regenerative fuel cells (RFCs), indicating reactions, underlying their advantages/disadvantages. We also underline the materials used for anode/cathode/electrolytes including perovskites (tunable), Au, Pt (costly), Pd, Ru, Ir, Ni, Ag, graphene, graphene oxide, carbon based, transition metal based, nanotechnological materials (NMs) including multiwalled nanotubes, nanorods, nanowires, nanosheets, core shell nanoparticles, nanofibers, carbon dots, quantum dots. The usage of NMs can address restrictions such as expensive materials that hinders commercialization and increase overall efficiency via effects including high surface area/size. Quantum dot NMs should play important roles in the fuel cell technology (addressing some of the challenges in the hydrogen production, storage, transportation, anode/cathode/electrolyte technology). The FCs have wide application range (stationary, mobile, portable) including applications in diversified areas such as electronic, power plants, passenger vehicles, housing, trucks, trains, unmanned aerial vehicles, submarines, aircrafts, three wheeled vehicles, industry, space shuttles, stationary energy generation, uninterrupted power supply, hybrid power, residential cogeneration, personal, wearable, portable power generators, mobile phones, laptops. Examples are given for simulation and artificial intelligence (AI) usage as important tools (artificial neural networks, particle swarm optimization ….) for design of improved cost, efficiency/performance, commercially accessible fuel cells, providing accurate diagnoses/quick data collection.