Surface polar charge induced Ni loaded CdS heterostructure nanorod for efficient photo-catalytic hydrogen evolution

Abstract

Designing of artificial heterostructure photo-catalysts to crop solar energy for H2 evolution from water is of great importance nowadays. The ultrafine Ni (0.5, 1.0, 2.0 and 5.0 wt%) particles loaded CdS nanorods were synthesized by a simple chemical process. XRD shows the crystalline phase of CdS with increase in size from 17 to 28 nm with 10.19% and 10.06% enhancement in the lattice strain and the dislocation density for Ni (0.5–5.0 wt%). The XPS peaks observed at 854.88 eV and 861.07 eV for Ni2+ with energy separation of 6.18 eV confirmed the existence of NiO on Ni surface. The Raman bands for pure CdS and Ni (1.0 wt%)-CdS nanorods were observed at 300 cm−1 and 293 cm−1 for 1LO phonon and 601 cm−1 and 586 cm−1 for 2LO phonon, respectively. The Ni loading tuned the CdS band gap from 2.36 to 2.20 eV. The eight fold enhancement in the CdS specific surface area i.e., from 4.19194 m2 g−1 to 34.8343 m2 g−1 was achieved. After Ni loading, the synergetic effect of efficient electron separation and transportation was observed by the continuous quenching of luminescence emission intensity and the reduction of charge transfer resistance from 706 Ω for CdS to 484 Ω of CdS. The Ni (1.0 wt%)@ NiO optimal loading on CdS results highest photo-catalytic H2 evolution of 9.0 mmol at rate of 1.8 mmol h−1, which is about 50 times higher than that of 180 μmol at rate of 36 μmol h−1 for pure CdS. A thin layer of NiO on plasmonic Ni surface could be the promising system for photo-catalytic H2 evolution due to visible light photo-activity.