Efficient p ‐ InP ( Rh ‐ H alloy ) and p ‐ InP ( Re ‐ H alloy ) Hydrogen Evolving Photocathodes

The solar to chemical energy conversion efficiencies of hydrogen generating photoelectrolytic cells with (Rh‐H alloy) and (Re‐H alloy) photocathodes have been increased, respectively, to 16.2% and 14.4%, as calculated from the electrical energy conserved in the photoassisted electrolysis of . Based on the electrical energy produced from the photoelectrochemically generated hydrogen in an ideal fuel cell operating at the thermodynamic potential, the solar to chemical conversion efficiences are, respectively, 13.3% and 11.4%. The cells were improved by increasing the barrier at the junction by hydrogen saturation, while maintaining the recombination passivating layer of hydrated indium oxide at pores in the thin, light transmitting metallic catalyst layer.