In situ/photoinduced fabrication of Zn/ZnO nanoscale hetero-interfaces with concomitant generation of solar hydrogen

Abstract

In the present investigation, we report the formation of a metal–metal oxide (Zn/ZnO) nanoscale heterointerfac with concomitant hydrogen generation. The synthesis process is simple and involves the optical illumination of Zn nanoparticles (Zn(NP)) suspended in water. The concomitant hydrogen (H₂) evolution during synthesis was found to be linear, and it is dependent on the growth of the Zn/ZnO nano interface. The progressively increasing amount of ZnO relative to Zn(NP) was a limiting factor in H₂ evolution. Two different Zn/ZnO nanoscale heterointerfaces were created and samples were extracted at two different stages of the illumination process. The first sample, extracted from the most reactive illumination phase and named Zn(NP)/ZnO-R, had the highest hydrogen evolution reaction (HER) rate. The second sample, extracted from a less reactive illumination phase and named Zn(NP)/ZnO-S, had a lower HER rate. These in situ (solar light-induced) samples were characterized by XRD, HRTEM, and other methods. The optoelectronic features and the photoelectrochemical (PEC) investigations showed the optimal light-harvesting ability of Zn(NP)/ZnO-R and the effective separation of photoexcited charge carriers, leading to remarkable HER performance. During the visible-light-induced (in situ) conversion of Zn(NP) to Zn(NP)/ZnO-R, a concurrent HER rate of 1115 μmol h⁻¹ was observed. Indeed, the photocurrent density value of the Zn(NP)/ZnO-R catalyst is significantly higher than that of Zn(NP)/ZnO-S, pristine Zn(NP), and ZnO. Thus, this study provides new insights into the optimal fabrication of the Zn(NP)/ZnO interface for PEC application with concomitant solar hydrogen generation.