Hetero-Janus Nanofibers as an Ideal Framework for Promoting Water-pollutant Photoreforming Hydrogen Evolution

Photoreforming hydrogen evolution (Pr-HE) of a water-pollutant system could simultaneously achieve efficient hydrogen production and pollutant degradation. It provides a new way to solve energy and environmental issues, but the poor internal charge separation still limits its performance. This work designed hetero-Janus nanofibers (HJNFs) with ordered electric field distribution and separated redox surfaces to promote Pr-HE of the water-pollutant system. Taking ZnO/NiO heterojunction as an example, the hetero-Janus structures were prepared via "Dual-channel" electrospinning and further confirmed by the element morphology analysis and asymmetric distribution of the XPS spectra. The theoretical simulation showed that Janus structures could effectively inhibit the electron trap and hole trap generation, then accelerate the directional carrier migration to the surface. Experimental investigations also confirmed that Janus structures could effectively suppress internal exciton luminescence and accelerate surface charge transfer. The Pr-HE amount and the corresponding propranolol (PRO) degradation rate of HJNFs were 7.9 and 1.5 times higher than hetero-mixed nanofibers (HMNFs). The enhancement factor of Pr-HE in water-PRO to pure water was about 3.1, but nearly zero for HMNFs. This prominent synergistic effect was due to the enhancement of charge separation and the inhibition of cascade side reaction from hetero-Janus structures. Furthermore, the synchronous Pr-HE and degradation reactions were significantly promoted by selective introducing Ag nanoparticles in one side of the HJNFs for enlarging the interfacial Fermi energy level difference. The hetero-Janus strategy offers a new perspective on designing efficient photoreforming photocatalysts for energy and environment applications.