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Publication costs assisted try Colorado State UniversityPhotosynthetic production of H2 and H202 is demonstrated on UV-irradiated ZnO/water and Ti02/water suspensions. The rates of H2 and H202 production were monitored by a combined analytical-gas chromatographic procedure as a function of irradiation time and solid content. In the case of ZnO, evidence is presented which indicates that photocorrosion of ZnO proceeds simultaneously with photosynthesis of H2 and HzOD The present data are rationalized with the aid of energy band diagrams showing the relative positions of the semiconductor band edges and the solution redox levels. IntroductioinThere has lbeen much recent interest in photocatalytic and photosynthetic processes at the a,emiconductor/liquid interface-l Interest in photosynthetic processes stems primarily from the possibility of utillizing these reactions to convert sunlight to storable forms of energy. Two reactions which have received particular attention in this regard are Both of these reactions are thermodynamically "uphill" and involve respectively free-energy changes of 2.43 and 1.26 eV per molecule. Photoelectrochemical (PEC) methods h a w offered a ready means of overcoming the thermodynamic barriers and have einabled production of fuels by reactions 1 and 2. Several rleviews of this field of research have appeared in the recent literaturea2 An attractive alternative to the PEC approach involves the socalled photoriynthetic m0de.l' This approach utilizes semiconducting grains which are suspended in the appropriate reaction media and thereby affords a more practical means of carrying out the energy conversion process. Each illuminated grain may be regarded as a short-circuited PEC cell, and the reactions at the interface of each grain and the liquid medium constitute the "local cell"ld,fJ processes.Photosynthetic production of Hz02 according to reaction 2 has been investigated on various semiconducting materials including ZnO?s5 CdS,4 HgS: ZnS,4 CdTe,6 CdSe,4 and Ga2S3.4 ZnO, in particular, has been the focus of considerable a t t e n t i~n .~,~ Notwithstanding the controversies that remain on the mechanism of photosynthesis of Hz02 at the ZnO/liquid i~i t e r f a e e ,~~ it was particularly of interest to note that previous authors had reported no traces of hydrogen in the reaction products.3c In view of the importance of reaction 1 to energy conversion and storage and the preponderance of this reaction at oxide semiconductor/electrolyte interfaces in general (vide infra), we decided to reexamine the products of UV-generated processes at the powdered ZnO/liquid interface.A second aspect of relevance to this paper concerns reaction 2. Pirevious authors had observed H202 production at the Ti02/electrolyte interface subjected to UV and visible irradiation.6 These experiments were, however, conducted in the photoelectrochemical mode. With powdered Ti02 grains suspended in aqueous solution, no evidence for reaction 2 was obtained in previous studies.3a This finding was surprising particularly in vie...

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The reactivity of the mono‐, di‐ and trimethyl‐ammonium nitrates to heat has been studied using differential thermal analysis, thermogravimetry and mass spectral analysis. The decomposition temperature of these compounds increases in the order CH3NH3NO3 > (CH3)2NH2NO3 > (CH3)3NHNO3. The activation energies have been determined employing isothermal decomposition technique. Mass spectrometric investigation shows that the extent of decomposition increases with increasing substitution on the nitrogen atom. Possible reasons for such behaviour have been explored.

Coloration in polyacrylonitrile can be induced in three distinct ways: by heat treatment, by treatment with base, or during synthesis of the polymer itself using ionic initiators at relatively higher temperatures. The present investigation employing and 13C NMR spectroscopy has revealed some common features in colored polyacrylonitrile irrespective of its mode of coloration. All colored polyacrylonitriles give an additional peak around 2.7 in NMR spectra and, except for heat-treated polyacrylonitrile, one extra group of peaks in the region 12-16 in 13C NMR spectra. The former peak has been attributed to methine and/or methylene protons in branched and/or cyclized structures, while the latter peak has been attributed to methylene carbon atoms in the branched structure. Colorless polyacrylonitriles have been found to be predominantly heterotactic, while colored polyacrylonitriles have been found to have appreciable isotactic contribution.