Hydrogen is the simplest and most abundant chemical element in our universe— it is the power source that fuels the Sun and its oxide forms the oceans that cover three quarters of our planet. This ubiquitous element could be part of our urgent quest for a cleaner, greener future. Hydrogen, in association with fuel cells, is widely considered to be pivotal to our world’s energy requirements for the twenty-first century and it could potentially redefine the future global energy economy by replacing a carbon-based fossil fuel energy economy. The principal drivers behind the sustainable hydrogen energy vision are therefore: • the urgent need for a reduction in global carbon dioxide emissions; • the improvement of urban (local) air quality; • the abiding concerns about the long-term viability of fossil fuel resources and the security of our energy supply; • the creation of a new industrial and technological energy base—a base for innovation in the science and technology of a hydrogen/fuel cell energy landscape. The ultimate realization of a hydrogen-based economy could confer enormous environmental and economic benefits, together with enhanced security of energy supply. However, the transition from a carbon-based(fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological, and socio-economic barriers. These include: • low-carbon hydrogen production from clean or renewable sources; • low-cost hydrogen storage; • low-cost fuel cells; • large-scale supporting infrastructure, and • perceived safety problems. In the present chapter we outline the basis of the growing worldwide interest in hydrogen energy and examine some of the important issues relating to the future development of hydrogen as an energy vector. As a ‘snapshot’ of international activity, we note, for example, that Japan regards the development and dissemination of fuel cells and hydrogen technologies as essential: the Ministry of Economy and Industry (METI) has set numerical targets of 5 million fuel cell vehicles and10 million kW for the total power generation by stationary fuel cells by 2020. To meet these targets, METI has allocated an annual budget of some £150 million over four years.
[NiFe], [FeFe], and [Fe] hydrogenase models from isomers
