Challenges of separating "solar fuels"
To limit climate change, we must meet our energy needs without increasing atmospheric carbon dioxide (CO2). Although still at an early stage, (photo)electrochemical CO2 reduction (“solar fuels”) offers potentially scalable and transformative technology to make fuels and chemicals.
However, product separation and its energy requirements are a critical and often overlooked challenge. While proven and effective, distillation is energy intensive; more efficient methods (e.g., solvent extraction, membranes, and other approaches) are useful but often less selective and not universally applicable. With currently known technology, the energy return on energy investment sustainability metric could be low or even below one. Identifying major contributing factors may help focus research on critical areas, such as trade-offs between product selectivity and overall efficiency, and facilitate interaction between catalysis and separations researchers to help solve the challenges of making solar fuels. These topics are covered in an article written by Jeffery Greenblatt and colleagues and published in the journal Joule in February.