Overcoming Metabolic & Efficiency Limits of Natural Photosynthesis: The Current Status and Future of Artificial Photosynthesis
Universal rules govern the efficiency of metabolic processes among all organisms in the tree-of-life (ToL), including natural photosynthesis. The latter efficiency is very low, below 1% solar to biomass conversion. This inefficiency is inherent in the disparate timescales of photonic conversion vs biochemical reactions. The large-scale use of low efficiency energy crops is the greatest threat to Earth’s ecosystems and human survival in the near term.
In this talk, I will highlight two projects one each from natural and artificial photosynthesis. The first successful effort to replace manganese in Nature’s water oxidation catalyst (Mn4CaO5) in Photosystem II with cobalt, will illustrate the chemical principles how these elements oxidize water and why manganese is universally adopted biologically across the ToL.
In contrast to natural photosynthesis, the steps in artificial photosynthesis operate at closer timescales, achieving higher solar-to-chemical conversion efficiency, but have made far simpler products until recently. Creation of energy efficient electrochemical CO2 reduction (CO2RR) catalysts that are product selective is the most important unrealized step in achieving a truly closed-loop carbon economy based on recycling CO2. Biology has evolved 6 distinct enzymes for CO2 reduction in different environments from which to learn their chemical principles. Starting from a knowledge of catalysis by these enzymes, we have developed a new family of abiotic electrocatalysts using binary nickel phosphide compounds (NixPy) that unlock an efficient multi-proton, multi-electron electrolysis pathway that converts water and CO2 into C1, C2, C3, C4 and C5 carbohydrates at ambient temperature and exceptional energy efficiency (93-99%). I will present the fundamental chemistry and point to current efforts at scaling-up the technology.
~Coffee/tea will be served prior to lecture~