Manipulating Photoconduction\nin Supramolecular Networks\nfor Solar-Driven Nitrate Conversion to Ammonia and Oxygen

For photoelectrodes to be used in practical catalytic\napplications,\nchallenges exist in achieving the efficient production and transport\nof photogenerated charge-separated states. Analogous concepts in traditional\ninorganic photoelectrodes can be applied to their organic-polymer\ncounterparts with improved charge-separation efficiencies. In this\nwork, we develop photoconductive organic networks to form a high-performance\nphotoelectrode for NO<sub>3</sub><sup>–</sup> reduction to\nNH<sub>3</sub>. In the integrated network, interfaces between the\norganic electron-donating photoconductor and electron-accepting catalyst\ncan generate charge carriers efficiently upon illumination, leading\nto enhanced charge separation for photoelectrocatalysis. The photoelectrode\nnetwork is capable of converting NO<sub>3</sub><sup>–</sup> to NH<sub>3</sub> at an external quantum efficiency of 13%. By coupling\nwith a BiVO<sub>4</sub> photoanode in tandem, the system reduces NO<sub>3</sub><sup>–</sup> to NH<sub>3</sub> and oxidizes H<sub>2</sub>O to O<sub>2</sub> simultaneously at Faradaic efficiencies of 95–98%\nwith sustained photocurrents and production yields. Investigation\nof the photoconductive network by steady-state/time-resolved spectroscopies\nreveals the efficient generation and transport of free charge carriers\nin the photoelectrode, providing a basis for high photoelectrocatalytic\nperformances.