Fuel Cells

In the image is an acidic hydrogen fuel cell. Which electrode is the arrow pointing to?

• Negative electrode

• Positive electrode

In the image is an acidic hydrogen fuel cell. The half reaction occurring at the identified electrode is...

• O₂ (g) + 4H⁺ (aq) + 4e^- → 2H₂O (l)

• O₂ (g) + 2H₂O (l) + 4e^- → 4OH^- (aq)

• H₂ (g) → 2H⁺ (aq) + 2e^-

• H₂ (g) + 2OH^- (aq) → 2H₂O (l) + 2e^-

In the image is an acidic hydrogen fuel cell. The half reaction occurring at the identified electrode is...

• O₂ (g) + 4H⁺ (aq) + 4e^- → 2H₂O (l)

• O₂ (g) + 2H₂O (l) + 4e^- → 4OH^- (aq)

• H₂ (g) → 2H⁺ (aq) + 2e^-

• H₂ (g) + 2OH^- (aq) → 2H₂O (l) + 2e^-

In the image is an acidic hydrogen fuel cell. The electrode the arrow is pointing to is the...

• Positive electrode

• Negative electrode

The half-equation for the reaction occurring at the (+) electrode in a hydrogen-oxygen fuel which has an alkaline electrolyte would be

• H₂(g) + 2OH^-(aq)→ 2H₂O(l) + 2e^-
• H₂(g) → 2H⁺(g) + 2e^-
• O₂(g) + 4H⁺(aq) + 4e^- → 2H₂O(l)
• O₂(g) + 2H₂O(l) + 4e^- → 4OH^- (aq)

A simplified diagram of the phosphoric acid fuel cell (PAFC), and their half-reactions are shown. The cell operates at 190^oC using an electrolyte of liquid phosphoric acid.
During operation of the PAFC, electrode I is

• positively charged, and the pH near the electrode will increase
• positively charged, and the pH near the electrode will decrease
• negatively charged, and the pH near the electrode will increase
• negatively charged, and the pH near the electrode will decrease

A simplified diagram of the phosphoric acid fuel cell (PAFC), and their half-reactions are shown. The cell operates at 190^oC using an electrolyte of liquid phosphoric acid.
Consider the following statements in regards to the PAFC:
I. The electrodes are likely to be porous and have a catalytic function.
II. More electrical energy will be produced in the PAFC for an equivalent mass of hydrogen, than using the fuel to produce steam for the generation of electricity by a turbine and generator.
III. The water generated in the cell reaction will dilute the electrolyte progressively and lower the efficiency of the cell.
Which of the above statements about PAFC are correct?

• I and II only
• I and III only
• II and III only
• I, II and III

Methane gas is used as a fuel in an acidic fuel cell. The half-equation occurring at the anode will be

• O₂(g) + 4H⁺(aq) + 4e^- →2H₂O(g)
• CH₄(g) + 2H₂O(g) → CO₂(g) + 8H⁺ (aq) + 8e^-
• CH₄(g) + 4H⁺(g)→ CO₂(g) + 4H₂O(l)
• CO₂(g) + 8H⁺(aq) + 8e^- → CH₄(g) + 2H₂O(g)

In a fuel cell based on the oxidation of methane, the equation for the anode half-reaction is:
CH₄(g) + 2H₂O(l) → CO₂(g) + 8H⁺(aq) + 8e^-
The corresponding equation for the half-reaction at the cathode is

• 2H₂O(l) + 4e^- → 4H⁺(aq) + O₂(g)
• 4H⁺(aq) + O₂(g) → 2H₂O(l)
• 2H₂O(l) → 4H⁺(aq) + O₂ (g) + 4e^-
• 4H⁺(aq) + O₂(g) + 4e^- → 2H₂O(l)

A fuel cell currently under development for powering small electronic devices is based on the reaction of methanol and oxygen using an acidic electrolyte. The reductant in the cell reaction and the half-reaction at the anode are

• Methanol; O₂(g) + 4H⁺(aq) + 4e^- → 2H₂O(l)
• Oxygen; O₂(g) + 4H⁺(aq) + 4e^- → 2H₂O(l)
• Methanol; CH₃OH(g) + H₂O(l) → CO₂(g) + 6H⁺(aq) + 6e^-
• Oxygen; CH₃OH(g) + H₂O(l) → CO₂(g) + 6H⁺(aq) + 6e^-