Contemporary models are shown to significantly underestimate the attainable efficiency of solar energy conversion to water splitting, and experimentally a cell containing illuminated AlGaAs/Si RuO2/Ptblack is demonstrated to evolve H2 and O2 at record solar driven water electrolysis efficiency. Under illumination, bipolar configured Al0.15Ga0.85As (E g = 1.6 eV) and Si (E g = 1.1 eV) semiconductors generate open circuit and maximum power photopotentials of 1.30 and 1.57 V, well suited to the water electrolysis thermodynamic potential:  H2O → H2 + 1/2O2; E°H 2 O = E O 2 − E H 2 ; E°H 2 O(25 °C) = 1.229 V. The E°H 2 O/photopotential matched semiconductors are combined with effective water electrolysis O2 or H2 electrocatalysts, RuO2 or Ptblack. The resultant solar photoelectrolysis cell drives sustained water splitting at 18.3% conversion efficiencies. Alternate dual band gap systems are calculated to be capable of attaining over 30% solar photoelectrolysis conversion efficiency.

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Cryst. Res. Technol. 341999 10 1323-1328Vicker's microhardness study of (100), (010) and (001) faces of a non-linear optical crystal, L-arginine hydrobromide monohydrate (LAHBr)have been reported.(100) plane is found to be the weakest plane. It has been observed that the microhardness decreases with increasing load for the three crystal planes. The microhardness behaviour have been explained successfully with the help of the PSR model proposed by Li and Bradt. Work hardening index n for the three planes are found to be greater than 1.6 which indicates that LAHBr is a soft crystal.

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Efficient Solar Water Splitting, Exemplified by RuO 2 -Catalyzed Al-GaAs/Si Photoelectrolysis.-A solar photoelectrolysis cell containing AlGaAs/Si RuO 2 /Pt black is demonstrated to drive sustained water splitting at 18.3% conversion efficiency. This value is higher than the efficiencies predicted by the principal solar water splitting models. -(LICHT, S.; WANG, B.; MUKERJI, S.; SOGA, T.; UMENO, M.; TRIBUTSCH, H.; J.

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