Selective Carbon Dioxide Reduction Catalyzed by Single Cobalt Sites on Carbon Nitride Under Visible-Light Irradiation (UNH 2019-025)

Background

A great deal of research is focused on realizing a green energy technology which can convert carbon dioxide (CO2) into useful fuels in an environmentally sound manner. One specific area of interest is utilizing sunlight as the energy input for such processes. The goal is to develop efficient photocatalysts based on earth‑abundant elements that can reduce CO2 into energy‑rich chemicals and fuels under visible light irradiation. Currently, there are no commercially available products of this sort. While metal‑ligand complexes have been used as catalysts in many reactions, they are often expensive and difficult to prepare.

Technology

Researchers at Stony Brook University (SBU) propose a composition of a photocatalyst, a method of manufacturing the photocatalyst, and a method of chemically reducing carbon dioxide (CO2) to carbon monoxide (CO) using the photocatalyst under visible‑light irradiation. The photocatalyst comprises single cobalt sites deposited on graphitic carbon nitride. The cobalt (Con+), in absence of additional ligands, forms coordinate bonds with nitrogen atoms in the graphitic carbon nitride where the nitrogen atoms maintain a flat plane framework. In one embodiment, the COn+ is CO2+. The method for manufacturing this photocatalyst includes preparing a mixture of graphitic carbon nitride and a cobalt salt in a polar solvent, forming a cobalt‑carbon nitride complex. The method provided for chemically reducing CO2 includes dispersing a photocatalyst in a polar solvent, introducing CO2 into the dispersion, and irradiating the CO2-containing dispersion with visible light (provided by solar radiation or a halogen lamp), thus reducing the CO2 to yield CO. The method also includes recycling the photocatalyst. This composition demonstrates excellent activity in cleanly converting CO2 into carbon‑based fuel CO under visible light using earth‑abundant materials.

Advantages

Earth‑abundant materials - Inexpensive to produce - Selective - Excellent activity under visible‑light irradiation - Low cobalt loading (shows more activity under visible light than high loading) - More material is not needed - Scalable - Recyclable catalyst