Impact of Silicon Resistivity on the Performance of Silicon Photoanode for Efficient Water Oxidation Reaction

Exploitation of efficient water oxidation catalysts with cost effectiveness and high activity is a prerequisite to enable water splitting as an alternative pathway for a renewable energy source. Silicon has the potential for high efficiency oxygen evolution reaction (OER). However, an important factor, which is the doping concentration of the silicon influence on the OER performance, has not been studied. Our results show that the performance of the silicon photoanode is significantly influenced by its resistivity, which is directly related to the doping concentration. In combination with ultrathin NiFe alloy nanoflakes (2 nm thick) deposited by the electron beam evaporation method, a NixFe(1-x)/TiO2/n-Si photoanode for water oxidation has been demonstrated. Our results show that the prepared Ni80Fe20/TiO2/n-Si photoanode with Si resistivity of 0.5 Omega.cm(-1) exhibits high catalytic performance with a low onset potential of 1.06 V versus RHE (eta(0) = -0.17 V), which are comparable to the state-of-the-art photoanodes using Ir or Ru as a catalyst. In addition, the photocurrent density at the reversible potential for water oxidation (1.23 V versus RHE) is around 21.5 mA.cm(-2), which is higher than most of the metal/TiO2/n-Si photoanodes. Therefore, our Ni80Fe20/TiO2/n-Si (0.5) photoanode shows great potential to replace precious metals for highly efficient large-scale water splitting.