Non-Uniform Deposition of N‑CoP₃ Films on Silicon-Based Photoelectrodes for Efficient Water Splitting

Photoelectrochemical water splitting is one of the most promising means of hydrogen production. Micro-/nanostructured silicon (Si) is beneficial to reduce the light reflection on the electrode surface to enhance the utilization efficiency of solar energy. However, the multiple reflection of light in the micro-/nanostructure on the Si surface will increase the parasitic light absorption by cocatalysts. In this work, the 3D black Si with micro-pyramids and nanopores was obtained, which anti-reflective structure can improve light absorption. Meanwhile, the non-uniform deposition of N-CoP₃ on 3D black Si can be induced by the micro-pyramid structure, minimizing the parasitic light absorption of N-CoP₃ and improving the photoelectrochemical performance of the 3D black Si/N-CoP₃ photoelectrode. The designed photoelectrode can achieve a high onset potential of 0.315 V versus RHE and a photocurrent density of −21.8 mA cm^–2 at 0 V versus RHE. Meanwhile, the 3D black Si/N-CoP₃ exhibits >10 h stability under simulated 100 mW cm^–2 (1 sun) with an AM 1.5G filter in 0.5 M H₂SO₄ at 0 V versus Ag/AgCl.