A concerted investigation of the interlayer charge transfer in Silver/Anatase nanocomposites

The use of hybrid nanomaterials, characterized by unprecedented behaviors and features, has now paved the way toward promising applications in many fields, such as electrocatalysis, photocatalysis, electroanalysis, and environmental chemistry, impacting on the everyday life [1]. Suitably designed nanoheterojunctions enhance synergistic functionalities and allow one to obtain “brave new materials” with physicochemical properties that are not simply the addition of the precursors’ ones but are completely new, different, and unexpected. However, research on such devices is most often dominated by trial and error procedures, while a deep atomistic understanding of the phenomena inside of the junction region driving appropriate design of the final device is missing. Here, a concerted theoretical and electrochemical investigation is proposed to gain insights into the important class of heterojunctions made by metal-semiconductor interfaces. Specifically, this approach is applied to the case of silver/anatase hybrid nanocomposite, a very promising material for advanced sensing applications [2]. In particular, we measure the exceptional electrochemical virtues of the Ag/TiO2 junction in terms of current densities and reproducibility, providing their explanation at the atomic-scale level and demonstrating how and why silver acts as a positive electrode [3]. Using periodic plane-wave DFT calculations, we estimate the overall amount of electron transfer toward the semiconductor side of the interface at equilibrium. Suitably designed (photo)electrochemical experiments strictly agree, both qualitatively and quantitatively, with the theoretical charge transfer estimates. The unique permanent charge separation occurring in the device is possible because of the synergy of Ag and TiO2, which exploits in a favorable band alignment, in a smaller electron–hole recombination rate and in a reduced carrier mobility when electrons cross the metal–semiconductor interface. Finally, the hybrid material is proven to be extremely robust against aging, showing complete regeneration, even after 1 year [3]. [1] A.V. Emeline, V.N. Kuznetsov, V.K. Ryabchuk, and N. Serpone, Environ. Sci. Pollut. Res. 19 (2012) 3666–3675. [2] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, and L. Falciola, Analyst 140 (2015) 1486–1494. [3] G. Di Liberto, V. Pifferi, L. Lo Presti, M. Ceotto, and L. Falciola, J. Phys. Chem. Lett. 8 (2017) 5372–5377.