High‐Performance Si Photocathode Enabled by Spatial Decoupling Multifunctional Layers for Water Splitting

Spatial decoupling of light absorption and catalytic reaction is a promising approach to improve the efficiency and stability of Si photoelectrodes. Herein, patterned Ag dots (PADs) are fabricated as the front electrode on a glass layer on commercial SiNx‐coated monocrystalline p‐n+ Si by an industrial manufacture strategy. It is found that the electron tunneling glass layer offers excellent protection to Si photocathode in an acidic electrolyte (0.5 M H2SO4). The SiNx layer for antireflection and surface passivation also resists the corrosive electrolyte. Under 1 sun (AM 1.5G) illumination, PADs‐decorated photocathode with a 0.75 mm dot‐spacing exhibits a saturation photocurrent of 36.1 mA cm−2 and a photovoltage of 0.61 V when Pt is electrodeposited as the hydrogen evolution catalyst on PADs. The applied bias photo‐to‐current conversion efficiency (ABPE) reaches 9.7%. This performance is enabled by the simultaneous optimization of light absorption and collection of photoexcited electrons. The photocurrent can remain stable for about 100 h at 0 V versus the reversible hydrogen electrode (RHE). This study identifies a new combination of multifunctional spatial‐decoupling layers that is efficient in both light absorption, transfer of photoexcited electrons, and stable in an acidic electrolyte.