Highly Efficient NiFe Nanoparticle Decorated Si Photoanode for Photoelectrochemical Water Oxidation

Abstract

n-Si is a narrow band gap semiconductor that has been demonstrated as an excellent photoabsorber material for photoelectrochemical (PEC) water splitting. Depositing a thin layer of Ni film on n-Si can form a Schottky junction at the interface, which offers a simple and useful route toward light-driven water oxidation. However, the relatively low catalytic activity of the Ni layer and the presence of interface states limit the application of this structure. Herein, we prepared a high-performance NiFe nanoparticle decorated Si photoanode for efficient solar-driven water oxidation to O2. NiFe nanoparticles were dispersed on a Si substrate surface homogeneously to form an inhomogeneous metal–insulator–semiconductor (MIS) junction, which increased the photovoltage of the photoanode. In addition, the oxide/oxyhydroxide layer on the deposited NiFe layer formed during the evaporation deposition acted as a highly efficient electrocatalyst, which also contributed to the high PEC performance of the photoanode. The photoanode covered with a 2 nm NiFe film exhibited the best PEC performance with a low onset potential of 1.09 V versus reversible hydrogen electrode (RHE) (the potential required to reach the photocurrent of 1 mA/cm2), a high photocurrent of 25.2 mA/cm2 at 1.23 V versus RHE, and a stable output over 50 h under AM 1.5G illumination due to the high-performance inhomogeneous MIS junction and a thick oxide/oxyhydroxide catalytic shell formed on the NiFe nanoparticle via an aging process.

Quantifying Losses and Assessing the Photovoltage Limits in Metal–Insulator–Semiconductor Water Splitting Systems

“…Many insulators have been utilized in silicon‐based MIS photocatalyst systems. These include SiO 2 ,28–41 TiO 2 ,42–47 HfO 2 ,48,49 Al 2 O 3 ,42,50–53 SrTiO 3 ,54 and ZrO 2. 55 Initially, MIS systems were motivated by their ability to improve the chemical stability of semiconductors, but recently many design strategies have been identified to improve the efficiency of these systems.…”

Metal/semiconductor interfaces in nanoscale objects: synthesis, emerging properties and applications of hybrid nanostructures

“…222 In the eld of electrocatalysis various suldes, phosphides, nitrides, oxides and (oxy)hydroxides are common catalysts, which are deposited on a substrate that serves as the electrode and they enhance either or both the activity and stability (for example, due to higher stability than the Si substrate in a strong alkaline environment). [223][224][225][226][227] A common starting high-specic-surface-area metallic substrate is nickel foam (NF), on which gas-phase electrodeposition and a variety of solvothermal reactions are used to deposit the metallic catalyst. Various redox catalysts were deposited on NF such as binary Ni-based materials, e.g., Ni 2 P, 228 Mo-doped Ni 2 P, 229 ternary amorphous tungsten-doped Ni x P, 228 or multiphase nickel suldes, 230 taking advantage of the abundant Ni surface.…”

Si-Based Metal–Insulator–Semiconductor Structures with RuO2–(IrO2) Films for Photoelectrochemical Water Oxidation

“…Similarly, a 2 nm thick NiFe film was deposited on a silicon substrate which exhibited a photocurrent of 25.2 mA/ cm 2 at 1.23V versus RHE stable for over 50 h under an AM 1.5 G illumination due to the high performance of the inhomogeneous MIS junction. 8 A photovoltage as high as 500 mV was achieved for the Ir/TiO 2 /Si MIS structure in alkaline, neutral, and acid aqueous electrolyte solutions. 9 The thicknesses of the Ir and TiO 2 layers were 3 and 2 nm, respectively.…”

“…The Ni film provided protection against corrosion and catalyzed the oxygen evolution reaction (OER) as a nonprecious metal electrocatalyst. Similarly, a 2 nm thick NiFe film was deposited on a silicon substrate which exhibited a photocurrent of 25.2 mA/cm 2 at 1.23V versus RHE stable for over 50 h under an AM 1.5 G illumination due to the high performance of the inhomogeneous MIS junction . A photovoltage as high as 500 mV was achieved for the Ir/TiO 2 /Si MIS structure in alkaline, neutral, and acid aqueous electrolyte solutions .…”