Metal-Free Light Harvesters for Sustainable Solar Fuel Production

The accelerated consumption of fossil fuels and the concomitant rise in greenhouse gas emissions emphasize the need for transitioning towards renewable “green” resources. Solar-driven photocatalysis is a promising approach for mitigating simultaneously both the energy and environmental concerns.¹ However, the development of economically and environmentally sustainable processes creates the pressing need for new materials of low cost and toxicity, photocatalysts and co-catalysts, which enable and maintain substantial solar energy conversion efficiencies.<br/><br/>Carbon dots (CDs) and carbon nitride (CNx) can efficiently serve as metal-free photocatalysts for this purpose since they fulfil these requirements.^2-6 In particular, they are hydrophilic materials of low toxicity which are chemically and photochemically robust, can be synthesized at low cost, and show optimum photocatalytic properties upon pre-/nano-designed synthesis. In this work, we describe the synthesis of CN_x and CDs from low-cost organics and/or Earth abundant waste (circular economy), the structure of which bestow the derived photoabsorbers with distinctive photocatalytic performances. These light harvesters upon solar light irradiation, when combined with noble-metal free co-catalysts in aqueous photocatalytic systems, not only facilitate “green” fuel synthesis but also waste utilization to synthesize value-added chemicals. The use of waste materials also eliminates the need for additional sacrificial reagents traditionally used in great excess, which add to the overall cost of the process and result in toxic by-products.⁷ We anticipate that this approach could be a breakthrough in the development of “green”, scalable, economically and environmentally sustainable photocatalytic systems for solar fuel production.<br/><br/><b>References</b><br/>1. Kamat, P. V.; Bisquert, J., <i>J. Phys. Chem.</i> <i>C </i><b>2013</b>, <i>117</i>, 14873-14875.<br/>2. Achilleos, D. S.; Kasap, H.; Reisner, E.,<i> Green Chem.</i> <b>2020</b>, <i>22</i>, 2831-2839.<br/>3. Achilleos, D. S.; Yang, W.; Kasap, H.; Savateev, A.; Markushyna, Y.; Durrant, J. R.; Reisner, E., <i>Angew. Chem. Int. Ed.</i> <b>2020</b>, <i>59</i>, 18184- 18188.<br/>4. Kasap, H.; Achilleos, D. S.; Huang, A.; Reisner, E., <i>J. Am. Chem. Soc.</i><b> 2018</b>, <i>140</i>, 11604-11607.<br/>5. Kasap, H.; Godin, R.; Jeay-Bizot, C.; Achilleos, D. S.; Fang, X.; Durrant, J. R.; Reisner, E., <i>ACS Catalysis</i> <b>2018</b>, <i>8</i>, 6914-6926.<br/>6. Ren, J.; Achilleos, D. S.; Golnak, R.; Yuzawa, H.; Xiao, J.; Nagasaka, M.; Reisner, E.; Petit, T., <i>J. Phys. Chem. Lett </i><b>2019</b>, <i>10</i>, 3843-3848.<br/>7. Pellegrin, Y.; Odobel, F., <i>C. R. Chim.</i> <b>2017</b>, <i>20</i>, 283-295.