Organic photoelectrode engineering: accelerating photocurrent generation via donor-acceptor interactions and surface-assisted synthetic approach

Abstract

Conventional photoelectrocatalysts composed of precious metals and inorganic elements have limited synthetic design, hence, hampered modularity of their photophysical properties. Here, we demonstrate a scalable, one-pot synthetic approach to grow organic polymer films on the surface of the conventional copper plate under mild conditions. Molecular precursors, containing electron-rich thiophene and electron-deficient triazine-rings, were combined into a donor-acceptor pi-conjugated polymer with a broad visible light adsorption range due to a narrow bandgap of 1.42 eV. The strong charge push-pull effect enabled the fabricated donor-acceptor material to have a marked activity as an electrode in a photoelectrochemical cell, reaching anodic photocurrent density of 6.8 mu A cm(-2) (at 0.6 V vs. Ag/AgCl, pH 7). This value is 3 times higher than that of the model donor-donor thiophene-only-based polymer and twice as high as that of the analogue synthesized in bulk using the heterogenous CuCl catalyst. In addition, the fabricated photoanode showed a 2-fold increase in the photoelectrocatalytic oxygen evolution from water upon simulated sunlight irradiation with the photocurrent density up to 4.8 mA cm(-2) (at 1.0 V vs. Ag/AgCl, pH 14). The proposed engineering strategy opens new pathways toward the fabrication of efficient organic "green" materials for photoelectrocatalytic solar energy conversion.

Conventional photoelectrocatalysts composed of precious metals and inorganic elements have limited synthetic design, hence, hampered modularity of their photophysical properties. Here, we demonstrate a scalable, one-pot synthetic approach to grow organic polymer films on the surface of the conventional copper plate under mild conditions. Molecular precursors, containing electron-rich thiophene and electron-deficient triazine-rings, were combined into a donor-acceptor pi-conjugated polymer with a broad visible light adsorption range due to a narrow bandgap of 1.42 eV. The strong charge push-pull effect enabled the fabricated donor-acceptor material to have a marked activity as an electrode in a photoelectrochemical cell, reaching anodic photocurrent density of 6.8 mu A cm(-2) (at 0.6 V vs. Ag/AgCl, pH 7). This value is 3 times higher than that of the model donor-donor thiophene-only-based polymer and twice as high as that of the analogue synthesized in bulk using the heterogenous CuCl catalyst. In addition, the fabricated photoanode showed a 2-fold increase in the photoelectrocatalytic oxygen evolution from water upon simulated sunlight irradiation with the photocurrent density up to 4.8 mA cm(-2) (at 1.0 V vs. Ag/AgCl, pH 14). The proposed engineering strategy opens new pathways toward the fabrication of efficient organic "green" materials for photoelectrocatalytic solar energy conversion.