SEMICONDUCTOR ELECTRODES .34. PHOTOELECTROCHEMISTRY OF P-TYPE WSE2 IN ACETONITRILE AND THE P-WSE2-NITROBENZENE CELL

The photoelectrochemical behavior of p-type WSe//2 single crystal electrodes in acetonitrile solutions containing a number of redox couples left bracket e. g. , N,N,N prime ,N prime -tetramethyl-p-phenylene diamine ( plus 1/0), methyl viologen ( plus 2/ plus 1), nitrobenzene (0/ minus 1), phthalonitrile (0/ minus 1) right bracket was investigated. For couples with potentials in the bandgap region (ca. minus 0. 4 to plus 1. 0v vs. SCE), a linear increase of the photopotential with V//r//e//d//o//x was observed. Couples located at more negative potentials (i. e. , above the conduction bandedge) also showed a photoeffect, with the photopotential pinned at approximately 0. 95v; this was ascribed to surface state pinning or inversion. A PEC cell of the form p-WSe//2/PhNO//2, MeCN/Pt is described. Treatment of the p-WSe//2 electrode with iodide was shown to improve the efficiency of such cells.