Chapter 6D - Production of Green Hydrogen Flashcards
(25 cards)
Define Artificial Photosynthesis
Process that utilises human-made materials to capture hydrogen and oxygen by splitting water molecules.
Define Electrolyser
A device or system that houses the processes of electrolysing and manages the process flow of inputs and outputs.
Define Green Hydrogen
Hydrogen gas produced using renewable energy sources such as wind/solar power, through electrolysis of water
Define Photovoltaics
A device that connects/converts solar energy to electrical energy
Define Polymer Electrolyte Membrane
Uses proton conducting polymer membrane as the electrolyte and connects two half cells, but prevents mixing of different molecules
Why should we use Green Hydrogen?
- cleanest & environmentally friendly
- produced using renewable energy
- no carbon emissions
- can be used for transportation, industry and power generation
What are the limitations of Green Hydrogen?
- cost of renewable energy still high
- electrolysers have limited efficiency
- economic feasibility for large scale production
What are misconceptions surrounding PEM electrolysis?
- Carbon neutral
- Other technology e.g manufacture and transportation produce carbon dioxide emissions
What temperature does the PEM electrolyser operate at?
20 - 80 degrees celcius
Electrodes in a PEM electrolyser
- covered with platinum catalyst to increase gas production rate
Gas diffusion layers in a PEM electrolyser
- gold-lined, titanium and cabob paper
- distribute reactant gases evenly across electrode surface
Bipolar plates in a PEM Electrolyser
- prevent build up of current
- provides mechanical support
Polymer Electrolyte Membrane in a PEM cell
- selectively permeable to protons
- plastic polymer that is non-conductive
- block movement of other reactants
- prevents spontaneous reactions, increasing efficiency and decreasing contamination
What green chemistry principles does the PEM electrolyser consider?
- catalysis
- designing safer chemicals
- prevention of wastes
- use of renewable feedstocks
How is sunlight captured in artificial photosynthesis?
- human-made material absorb light to promote electrons to a higher energy state, producing around 2V
(electrical energy required to drive the reactions)
Nanowires in an artificial cell
- covered with different catalysts
- increase reaction rate of gas production
What are the stages of artficial photosynthesis?
- Light harvesting system
- Water oxidation
- Proton reduction
How does the production of green hydrogen benefit the environment?
- can be used to produce other industrial fuels, removing CO2 from the atmosphere (reduction in the presence of a catalyst)
What are the advantages of these production methods?
- does not create greenhouse gases
- does not use fossil fuels
- remove CO2 from atmosphere
- oxygen as a by-product
- can create green ammonia
What are the disadvantages of these production methods?
- materials are expensive
- not available on a large scale
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What are the factors of sustainability of green hydrogen?
- energy efficiency
- infrastructure
- cost
- water resources
Energy efficiency
- energy intensive
- costly renewable resources
Infrastructure
- limited infrastructure in producing, storing and transporting hydrogen
Cost
- Cost is higher than conventional fuels
- Limit use, especially in developing countries
