Thermochemical cycle | EPFL Graph Search

Thermochemical cycles combine solely heat sources (thermo) with chemical reactions to split water into its hydrogen and oxygen components. The term cycle is used because aside of water, hydrogen and oxygen, the chemical compounds used in these processes are continuously recycled. If work is partially used as an input, the resulting thermochemical cycle is defined as a hybrid one. This concept was first postulated by Funk and Reinstrom (1966) as a maximally efficient way to produce fuels (e.g. hydrogen, ammonia) from stable and abundant species (e.g. water, nitrogen) and heat sources. Although fuel availability was scarcely considered before the oil crisis efficient fuel generation was an issue in important niche markets. As an example, in the military logistics field, providing fuels for vehicles in remote battlefields is a key task. Hence, a mobile production system based on a portable heat source (a nuclear reactor was considered) was being investigated with utmost interest. Following the oil crisis, multiple programs (Europe, Japan, United States) were created to design, test and qualify such processes for purposes such as energy independence. High-temperature (around operating temperature) nuclear reactors were still considered as the likely heat sources. However, optimistic expectations based on initial thermodynamics studies were quickly moderated by pragmatic analyses comparing standard technologies (thermodynamic cycles for electricity generation, coupled with the electrolysis of water) and by numerous practical issues (insufficient temperatures from even nuclear reactors, slow reactivities, reactor corrosion, significant losses of intermediate compounds with time...). Hence, the interest for this technology faded during the next decades, or at least some tradeoffs (hybrid versions) were being considered with the use of electricity as a fractional energy input instead of only heat for the reactions (e.g. Hybrid sulfur cycle).

High-throughput parallel testing of ten photoelectrochemical cells for water splitting: case study on the effects of temperature in hematite photoanodes

Sophia Haussener, Isaac Thomas Holmes-Gentle, Franky Esteban Bedoya Lora, Roberto Valenza

High-throughput testing of photoelectrochemical cells and materials under well-defined operating conditions can accelerate the discovery of new semiconducting materials, the characterization of the phenomena occurring at the semiconductor-electrolyte inter ...

Royal Soc Chemistry2024

Enhanced Solar-to-Fuel Efficiency of Ceria-Based Thermochemical Cycles via Integrated Electrochemical Oxygen Pumping

Sophia Haussener, Clemens Gregor Suter, Meng Lin

The solar thermochemical cycle based on ceria is a promising route for renewable fuel production. The solar-to-fuel efficiency of a thermochemical reactor is highly dependent on the oxygen removal during the reduction step. Conventional nitrogen sweeping ( ...

AMER CHEMICAL SOC2022