High efficiency solar energy water splitting to generate hydrogen fuel:: Probing RuS2 enhancement of multiple band electrolysis

The conditions under which an oxygen photocatalyst can improve multiple band gap (semiconductor) solar energy water splitting are probed. Recently, we provided evidence that previous models significantly underestimated the magnitude of H-2 fuel which may be generated by solar energy, and demonstrated a bipolar band gap solar system electrolyzing water at V-H2O H2O --> H-2 + 1/2O(2); V-H2O > E degrees (H2O) = E degrees (O2) - E degrees (H2); E degrees (H2O)(25 degreesC) = 1.229 V at an unprecedented 18.3% solar energy conversion efficiency. Three conditions are shown in which oxygen photocatalyst addition can further improve this process; (i) a reduction in V-H2O (ii) at V-H2O. capability to sustain electrolysis currents greater than or equal to generated photocurrents, and (iii) catalyst activation at hv(photo-O2), > hv(photo-bipolar). We show that RuS2 with 1% Fe is capable of meeting these conditions. (C) 2002 Elsevier Science B.V. All rights reserved.