In the search for future energy supplies, the application of hydrogen as an energy carrier is seen as a prospective issue. However, the implementation of a hydrogen economy is suffering from several unsolved problems. Particularly challenging is the storage of appropriate amounts of hydrogen. In this context one of the promising hydrogen storage techniques relies on liquid-phase chemical hydrogen storage materials, in particular, aqueous sodium borohydride, ammonia borane, hydrazine, hydrazine borane and formic acid. The use of these materials in hydrogen storage provides high gravimetric and volumetric hydrogen densities, low potential risk, and low capital investment because it is largely compatible with the current transport infrastructure. In this review, we survey the research progresses in hydrogen generation from these liquid-phase chemical hydrogen storage materials and their regeneration.

Liquid-phase chemical hydrogen storage materials

A critical determinant of solar-driven water splitting efficiency is the kinetic profile of the O2 evolving catalyst (OEC). We now report the kinetic profiles of water splitting by a self-assembled nickel–borate (NiBi) OEC. Mechanistic studies of anodized films of NiBi exhibit the low Tafel slope of 2.3 × RT/2F (30 mV/decade at 25 °C). This Tafel slope together with an inverse third order rate dependence on H+ activity establishes NiBi as an ideal catalyst to be used in the construction of photoelectrochemical devices for water splitting. In contrast, nonanodized NiBi films display significantly poorer activity relative to their anodized congeners that we attribute to a more sluggish electron transfer from the catalyst resting state. Borate is shown to play two ostensibly antagonistic roles in OEC activity: as a promulgator of catalyst activity by enabling proton-coupled electron transfer (PCET) and as an inhibitor in its role as an adsorbate of active sites. By defining the nature of the PCET pre-equilib...

Mechanistic studies of the oxygen evolution reaction mediated by a nickel-borate thin film electrocatalyst.

Following a brief overview of the terrestrial distribution of boron in rocks, soil, and water, the history of the discovery, early utilization, and geologic origin of borate minerals is summarized. Modern uses of borate-mineral concentrates, borax, boric acid, and other refined products include glass, fiberglass, washing products, alloys and metals, fertilizers, wood treatments, insecticides, and microbiocides. The chemistry of boron is reviewed from the point of view of its possible health effects. It is concluded that boron probably is complexed with hydroxylated species in biologic systems, and that inhibition and stimulation of enzyme and coenzymes are pivotal in its mode of action.

An introduction to boron: history, sources, uses, and chemistry.

Boron-11 nuclear magnetic resonance spectroscopic study of borate and borosilicate minerals and a borosilicate glass

Interactions between boric acid derivatives and saccharides in aqueous media: Structures and stabilities of resulting esters

Spectres RMN de 11 B a 127 et 160 MHz de solutions aqueuses de KB 5 O 8 •4H 2 O, K 2 B 5 O 8 (OH)•2H 2 O, K 2 B 4 O 7 •4H 2 O et NaB 5 O 8 •5H 2 O. Separation des signaux et discussion des especes formees en fonction de la concentration

C. G. Salentine

Papers

High-field 11B NMR of alkali borates. Aqueous polyborate equilibria