Hydrogen Fuel Cell - AP Environmental Science

The transportation sector benefits. Vehicles can achieve zero local emissions using hydrogen power.

They produce no harmful emissions. Only water vapor is emitted, unlike fossil fuels that release greenhouse gases.

The proton exchange membrane (PEM). Selective permeability allows ionic conduction while blocking electrons.

It is energy-intensive and costly. Requires significant electrical input, making it expensive to operate.

Carbon dioxide (CO$_2$) is released. Burning fossil fuels produces CO$_2$ as a major greenhouse gas emission.

The proton exchange membrane (PEM). Selectively allows protons to pass while blocking electrons and gases.

Proton exchange membrane fuel cell (PEMFC). Low operating temperature and compact design suit automotive applications.

Platinum is expensive and scarce. High cost and limited supply make platinum catalysts expensive.

Electrolysis of water is common. Electric current splits water molecules into hydrogen and oxygen gases.

They conduct electrons and distribute gases. Manage electrical current flow and distribute reactant gases evenly.

Hydrogen and oxygen are essential. Hydrogen provides protons and electrons, oxygen accepts them to form water.

They provide water as a byproduct. Astronauts can drink the water produced as a valuable resource.

They reduce greenhouse gas emissions. Water vapor emission instead of CO$_2$ helps combat climate change.

Hydrogen gas is the main fuel component. Hydrogen gas provides the protons and electrons needed for the reaction.

The storage and transportation of hydrogen. Hydrogen is highly flammable and requires specialized containment systems.

Hydrogen has a higher energy density by weight. Hydrogen contains more energy per kilogram than gasoline.

Water is the byproduct. The only emission from the electrochemical reaction between hydrogen and oxygen.

An external circuit carries the electrons. Electrons flow through the external circuit to complete the electrical loop.

Chemical energy to electrical energy. Direct conversion without thermal combustion intermediates.

Around 80°C (176°F). Optimal temperature for efficient proton conduction in the membrane.

Approximately 0.7 volts per cell. Standard output for proton exchange membrane fuel cells under normal conditions.

$O_2 + 4H^+ + 4e^- \rightarrow 2H_2O$. Oxygen gains electrons and protons at the cathode to form water.

$2H_2 \rightarrow 4H^+ + 4e^-$. Hydrogen molecules lose electrons at the anode, becoming protons.

They are used in transportation, such as fuel cell vehicles. Cars, buses, and trucks can run on hydrogen fuel cells for zero emissions.

Carbon dioxide (CO$_2$) is released. Burning fossil fuels produces CO$_2$ as a major greenhouse gas emission.

$2H_2 + O_2 \rightarrow 2H_2O + \text{electricity}$. Shows hydrogen and oxygen combining to produce water and electrical energy.

Water vapor is the main component. Clean water vapor is the only emission from hydrogen fuel cells.

It speeds up the chemical reaction. Lowers activation energy needed for hydrogen oxidation and oxygen reduction.

Typically 40% to 60% efficient. Higher than internal combustion engines due to direct energy conversion.