Nat-HEC · Understanding Carbon-neutral Hydrogen Production by Nature’s Hydrogen Evolution Catalyst

Understanding Carbon-neutral Hydrogen Production by Nature’s Hydrogen Evolution Catalyst

Climate change is one of the biggest challenges faced by us as well as by future generations. Converting solar energy into chemical energy may be a promising perspective to reduce CO2 emissions. Here, energy is catalytically stored in chemical bonds. Following this principle, alternative fuels and chemical raw materials could replace fossil sources. However, catalysts composed of earth abundant elements that work at low over potential are necessary to accomplish this global challenge. Redox enzymes meet these requirements and catalyse in multi-electron reactions e.g. the fixation of nitrogen (N2, nitrogenase), carbon dioxide (CO- and formate-dehydrogenase), or the evolution of molecular hydrogen (H2, hydrogenases). Such enzymes serve as inspiring blueprints for the design of high-efficiency catalysts. The high energy density of H2 offers multiple possibilities for utilization as a carbon neutral fuel and chemical raw material. However, today about 95% of the industrially utilized H2 originates from steam reformation of fossil resources and is thus associated with significant CO2 release. This illustrates the need for alternative catalysts for hydrogen generation. Nature’s Hydrogen Evolution Catalyst, the redox enzyme [FeFe] hydrogenase, is found in both bacteria and algae. They catalyses the release of H2 with high rates, at neutral pH, and low overpotentials. [FeFe] hydrogenases inspired the design of numerous synthetic compounds mimicking its unique iron sulphur site, however never meeting the efficiency of the native system. The overall aim of the project is to elucidate the reaction mechanism of Nature’s Hydrogen Evolution Catalyst (Nat-HEC), the redox enzyme [FeFe] hydrogenase, to inspire the design of synthetic catalysts for the generation of molecular hydrogen (H2). Specific objectives are: Objective 1: The action aims to elucidate the catalytic mechanism of [FeFe] hydrogenases by transient absorption spectroscopy. Objective 2: In transient absorption spectroscopy experiments, ensemble samples have to be measured. Ideally, the reaction starts in all molecules of the ensemble at the same time from the same starting state. To approach this scenario, a homogenous starting state will be adjusted via a newly developed transmission cell. Objective 3: The reduction effectivity of photoinduced electron transfer will be optimized to enhance the signal to noise ratio, e.g. chemically altering or co-immobilizing photosensitizers and enzyme.

Data: CORDIS, © European Union