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

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 π-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 μA 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. We construct photoelectrodes based on a conjugated organic network. The donor-acceptor interactions within the polymer structure narrow the optical bandgap and enable efficient excited charge transfer, leading to the marked improvement of the PEC activity of the electrode.