Abstract

In the present investigation, we report the formation of metal-metal oxide (Zn/​ZnO) nanoscale heterointerface 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 rate (HER). The second sample, extracted from a less reactive illumination phase and named Zn(NP)/ZnO‑S, had a lower HER. 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 of 1115 μmol h‑1 was observed. Indeed, the photocurrent density value of Zn(NP)/ZnO‑R catalyst is significantly higher than that of Zn(NP)/ZnO‑S, pristine Zn(NP), and ZnO. Thus, the study provides new insights into the optimal fabrication of the Zn(NP)/ZnO interface for PEC application with concomitant solar hydrogen generation.