Interface engineering of the photoelectrochemical performance of Ni-oxide-coated n-Si photoanodes by atomic-layer deposition of ultrathin films of cobalt oxide

Introduction of an ultrathin (2 nm) film of cobalt oxide (CoOx) onto n-Si photoanodes prior to sputter-deposition of a thick multifunctional NiOx coating yields stable photoelectrodes with photocurrent-onset potentials of similar to -240 mV relative to the equilibrium potential for O-2(g) evolution and current densities of similar to 28 mA cm(-2) at the equilibrium potential for water oxidation when in contact with 1.0 M KOH(aq) under 1 sun of simulated solar illumination. The photoelectrochemical performance of these electrodes was very close to the Shockley diode limit for moderately doped n-Si(100) photoelectrodes, and was comparable to that of typical protected Si photoanodes that contained np(+) buried homojunctions.