Chapter 6D - Production of Green Hydrogen
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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 & most environmentally friendly form • produced using renewable energy • no carbon emissions • clean & sustainable fuel that 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 processes e.g. manufacture and transportation produce carbon emissions
What temperature does the PEM electrolyser operate at?
20 - 80 degrees celcius
Describe how the electrodes in a PEM cell maximise production of green hydrogen:
• covered w/ platinum catalyst • increases gas production rate
How do gas diffusion layers maximise the production of green hydrogen in a PEM electrolyser?
• made up of gold-lined titanium & carbon paper • helps to distribute reactant gases evenly across electrode surface
How do the Bipolar plates in a PEM electrolyser maximise the production of green hydrogen?
• prevents build up of current • provides mechanical support
How does the Polymer Electrolyte membrane in an PEM electrolyser maximise the production of green hydrogen?
• physical barrier 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 • promotes electrons to a higher energy state • produces around 2V (electrical energy required to drive the reactions)
Describe the nanowires in artificial photosynthesis
• 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?
• produce other industrial fuels, • remove CO₂ from the atmosphere (reduced in the presence of a catalyst)
What are the advantages of these green hydrogen 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 green hydrogen production methods?
• materials are expensive • not available on a large scale
What are the factors of sustainability of green hydrogen?
• energy efficiency • infrastructure • cost • water resources
Describe the energy efficiency of green hydrogen production:
• energy intensive • costly renewable resources
How does infrastructure affect the sustainability of using green hydrogen as an energy source?
• limited infrastructure in producing, storing and transporting hydrogen
How does cost affect the sustainability of green hydrogen use?
• cost is higher than conventional fuels • limit use especially in developing countries