Kinetically and Thermodynamically Favorable Ni–Al Layered Double Hydroxide/Ni-Doped Zn_0.5Cd_0.5S S-Scheme Heterojunction Triggering Photocatalytic H₂ Evolution

Layered double hydroxide (LDH)-based photocatalysts have attracted more attention in photocatalysis due to their low cost, wide band gaps, and adjustable photocatalytic active sites; however, their low photogenerated carrier separation efficiency limits their photocatalytic efficiency. Herein, a NiAl-LDH/Ni-doped Zn 0.5 Cd 0.5 S (LDH/Ni-ZCS) S-scheme heterojunction is rationally designed and constructed from kinetically and thermodynamically favorable angles. The 15% LDH/1% Ni-ZCS displays comparable photocatalytic hydrogen evolution (PHE) activity with a rate of 6584.0 μmol g –1 h –1, which exceeds by ∼6.14- and ∼1.73-fold those of ZCS and 1% Ni-ZCS, respectively, and outperforms most of the previously reported LDH-based and metal sulfide-based photocatalysts. In addition, the apparent quantum yield of 15% LDH/1% Ni-ZCS reaches 12.1% at 420 nm. In situ X-ray photoelectron spectroscopy, photodeposition, and theoretical calculation reveal the specific transfer path of photogenerated carriers. On this basis, we propose the possible photocatalytic mechanism. The fabrication of the S-scheme heterojunction not only accelerates the separation of photogenerated carriers but also decreases the activation energy of H 2 evolution and improves the redox capacity. Moreover, there are huge amounts of hydroxyl groups distributed on the surface of photocatalysts, which is highly polar and easy to combine with H 2 O with a large dielectric constant to form a hydrogen bond, which can further accelerate PHE.