Water splitting hydrogen

Water-Splitting Techniques. Only one water-sphtting method, electrolysis, is practiced industrially for the production of hydrogen, and that only to a limited extent. 

Direct, One-Step Thermal Water Splitting. The water decomposition reaction has a very positive free energy change, and therefore the equihbrium for the reaction is highly unfavorable for hydrogen production. 

Multistep Thermochemical Water Splitting. Multistep thermochemical hydrogen production methods are designed to avoid the problems of one-step water spHtting, ie, the high temperatures needed to achieve appreciable AG reduction, and the low efficiencies of water electrolysis. Although water electrolysis itself is quite efficient, the production of electricity is inefficient (30—40%). This results in an overall efficiency of 24—35% for water electrolysis. 

A detailed discussion of thermochemical water splitting is available (155,165—167). Whereas many problems remain to be solved before commercia1i2ation is considered, this method has the potential of beiag a more efficient, and hence more cost-effective way to produce hydrogen than is water electrolysis. 

Non-electrolytic sources of hydrogen have also been studied. The chemical problem is how to transfer the correct amount of free energy to a water molecule in order to decompose it. In the last few years about I0(X)0 such thermochemical water-splitting cycles have been identified, most of them with the help of computers, though it is significant that the most promising ones were discovered first by the intuition of chemists. 

Amides can add to aldehydes in the presence of bases (so the nucleophile is actually RCONH ) or acids to give acylated amino alcohols, which often react further to give alkylidene or arylidene bisamides. If the R group contains an a hydrogen, water may split out. 

Murphy AB, Barnes PRF, Randeniya LK, Plumb 1C, Grey IE, Home MD, Glasscock JA (2006) Efficiency of solar water splitting using semiconductor electrodes. Int J Hydrogen Energy 31 1999-2017... 

Sathish M, Viswanathan B, Viwanath RP (2006) Alternate synthetic strategy for the preparation of CdS nanoparticles and its exploitation for water splitting. Int J Hydrogen Energy 31 891-898... 

Zhou et al. obtained nitrogen-doped titanium dioxide replicas via a two-step infiltration process with natural leaves as templates [220]. The replicas inherited the hierarchical structures of the natural leaf at the macro-, micro-, and nanoscales. These materials showed enhanced light-harvesting and photocatalytic hydrogen evolution activities. The photocatalytic water splitting activity of the artificial leaf structures was eight times higher than that of titanium dioxide synthesized without templates. 

Khan, M.A. and Yang, O.B. (2009) Photocatalytic water splitting for hydrogen production under visible lighton Ir and Co ionized titania nanotube. Catalysis Today, 146 (1-2), 177-182. 

Kapoor, M.P., Inagaki, S.,and Yoshida, H. (2005) Novel zirconium-titanium phosphates mesoporous materials for hydrogen production by photoinduced water splitting. Journal of Physical Chemistry B, 109 (19), 9231-9238. 

Norman, J.H. et al., Thermochemical water-splitting for hydrogen production, Gas Research Institute report GRI-80/0105,1980. 

Kubo, S. et al., A demonstration study on a closed-cycle hydrogen production by thermochemical water-splitting Iodine-Sulfur process, Nucl. Eng. Des., 233, 347, 2004. 

Terada, A. et al., Development program of hydrogen production by thermo-chemical water splitting IS process, ICONE-13-50183, in Proc. 13th Int. Conf. Nucl. Eng., Beijing, China, May 16-20, 2005. 

Hydrogen, however, can be produced using sustainable technologies that are nowadays still not applied at large scale the most promising ones are water splitting by electrolysis using sustainably produced electricity (e.g., wind, hydro, and sun) and processes based on sustainable production and utilization of biomass.3... 

Efficiency of Hydrogen and Oxygen Generation by Water Splitting.244... 

For the operating voltage at the optimum power point Vp and the Faradaic current for water splitting of /p, the overall solar to hydrogen generation PV electrolysis efficiency is given by... 

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