ACS applied materials & interfaces | 2019
Highly efficient hydrogen and electricity production combined with degradation of organics based on a novel solar water-energy nexus system.
Abstract
A novel unassisted solar water-energy nexus system (SWENS) comprised of a monolithic photoanode, which was assembled by attaching a silicon cell (SC) at the reverse side of a high-activity hyaline antimony doped TiO2 nanorod array (Sb/TNR), and a Pt-black/Pt cathode, was proposed for effective electricity and hydrogen production accompanying with water treatment. The Sb/TNR with vertically arranged nanorods on F-doped SnO2 substrate, using a simple hydrothermal method, showed an excellently enhanced and stable photo-to-current density of ~1.77 mA cm-2 (0.6 V vs. Ag/AgCl), which is ~181% that of the undoped sample because antimony doping enhanced the charge transfer property and charge carrier density of Sb/TNR. The SWENS showed a removal ratio of nearly 100% for 2-chlorophenol after 4 h operation under AM 1.5 illumination, and achieved an average H2 production rate of 31.4 μmol h-1 cm-2 and an excellent electricity output with an open-circuit voltage of ~2.16 V, a short-circuit current of ~1857 μA cm-2, and a maximum power output of ~967 μW cm-2, which is ~10.8 times higher than the power density of the reported state-of-the-art photocatalytic fuel cell. This outstanding capability can be due to the synergistic effect of the monolithic photoanode, in which the prepositive Sb/TNR generates abundant electrons and holes using short-wavelength photons, and the SC provides much higher potential than traditional photocatalytic fuel cells to drive the electrons being transported to the cathode by absorbing the transmission of longer-wavelength photons. The results also revealed that the SWENS showed remarkably stability in long-term application and effective in clean energy production, while degrading various refractory organics. This work proposed a new effective way to develop composite water-energy nexus technology for simultaneous clean energy generation and water treatment.