A new strategy: fermi level control to realize 3D pyramidal NiCo-LDH/ReS2/n-PSi as a high-performance photoanode for the oxygen evolution reaction

Abstract

Loading ReS₂ nanosheets (NSs) on a planar p-type doping Si substrate has been proved to work well in photoelectrochemical (PEC) water splitting for the hydrogen evolution reaction (HER). The high PEC performance is attributed to the p–p junction for accelerating charge separation and the two dimensional (2D) light trapping effect for enhanced light absorption. Herein, we report a novel photoanode for the oxygen evolution reaction (OER) which is composed of an n-type pyramid-pattern Si substrate and p-ReS₂ NSs. Compared to planar ReS₂/p-Si, the p–n junction of ReS₂/n-PSi can achieve a much higher photocurrent due to more upward band bending, while more light absorption comes from the 3D anti-reflection structure. By avoiding near-surface downward band bending and enhancing charge transportation, the earth-abundant co-catalyst, NiCo-layered double hydroxides (NiCo-LDH), was finally deposited to boost the photocurrent of the NiCo-LDH/ReS₂/n-PSi photoanode into the competitive mA cm⁻² range (1.74 mA cm⁻²). The NiCo-LDH cover layer can also improve the stability of the photoanode by acting as a protective layer. Thus, it is a new concept for ReS₂/Si to work as a high-performance photoanode for the OER through Fermi level control and a split-new solution to deal with the energy barrier caused by the work function of different surface materials in a dual photoelectrode system.