New research published in Nature Communications introduces “Artificial Photosynthesis” or Water Splitting using photoelectrochemical devices(PEC), as a way to produce oxygen and Hydrogen, Carbon-based fuels, within the move to produce green energy transition on Earth.[1]
PEC devices are currently developed for sustainable solar-to-chemical energy conversion processes on Earth.
This technology is particularly being developed broadly for space travel, and particularly to help astronauts breathe on Mars.
Currently, about 1.5 kW out of the 4.6 kW energy budget of the Environmental Control and Life Support System(ECLSS) on the International Space Station (ISS) is consumed to produce Oxygen and clean water for the lab animals and astronauts.
The device would utilize semiconductor materials coated with metallic catalysts that support the 3 desired chemical reactions known as photocathode-driven hydrogen evolution reaction (HER), an anode-driven oxygen evolution reaction (OER), PEC water-splitting and carbon dioxide reduction reactions (CO2RR).
CO2RR has the added advantage of being able to generate hydrogen (H2) and various carbon-based fuels like methane (CH4), these fuels can be used in applications such as rocket propulsion (LOx/LCH4) or in the Fischer-Tropsch process for synthesizing other hydrocarbon-based fuels and chemicals.
$$2H_{2}O \rightarrow O_{2} + 4H^{+} + 4e^{-}(OER) \:\:\:\:\:\: E^{o} = -1.229V vs.RHE$$
$$2H^{+} + 2e^{-} \rightarrow H_{2} (HER) \:\:\:\:\:\: E^{o} = +0.00V vs.RHE$$
$$CO_{2} + 2H^{+} + 4e^{-}\rightarrow CO + H_{2}O\:\:\:\:\:\: E^{o} = -0.11V vs.RHE$$
$$CO_{2} + 8H^{+} + 8e^{-}\rightarrow CH_{4} + 2H_{2}O \:\:\:\:\:\: E^{o} = +0.17V vs.RHE$$
This process is similar to photosynthesis in plants, it utilizes water and sunlight and involves the separation of light harvesting from chemical production.
The device would lead to a substantial reduction in system weight and volume, it is way more efficient than the current ECLSS installed in the ISS, this is ideal for space travel since spacecraft can use sunlight to produce oxygen and water.
However, using this technique on Mars is questioned since Mars receives way less sunlight than Earth.
Further research and the use of solar mirrors are required to tackle this reduction in light intensity, the study states.
Katharina Brinkert, Assistant Professor, Department of Chemistry at the University of Warwick, who is a co-author of the study, stated “Human space exploration faces the same challenges as the green energy transition on Earth: both require sustainable energy sources. With sunlight being so abundantly available in space, we have shown how this source could be used to harvest energy – much like plants back on Earth – for life support systems for long-term space travel. The technology could provide ample oxygen production and carbon dioxide recycling on both Moon and Mars.”
References
- Byron Ross et al., ‘Assessment of the technological viability of photoelectrochemical devices for oxygen and fuel production on Moon and Mars’, Nature, 6 June 2023, “Human deep space exploration is presented with multiple challenges, such as the reliable, efficient and sustainable operation of life support systems. The production and recycling of oxygen, carbon dioxide (CO2), and fuels are hereby key, as a resource resupply will not be possible.”, https://www.nature.com/articles/s41467-023-38676-2[↩]
