Direct Borohydride Fuel Cell (DBFC)

The DBFC directly uses the NaBH₄ solution as the fuel filled in or continuously supplied to the anodic chamber,

In the system, the electricity is produced via the following anode and cathode reactions, as shown in Eqs. (1) and (2). The overall reaction of the system is shown in Eq.(3):

Schematic diagram of direct borohydride fuel cell (a top view)

NaBH₄+8OH⁻-->NaBO₂+6H₂O+8e⁻ (anode), E°=−1.24 V vs. SHE                           (1)

2O₂+4H₂O+8e⁻-->8OH⁻ (cathode), E°=0.40 V vs. SHE                                          (2)

NaBH₄+2O₂-->NaBO₂+2H₂O (overall), E°=1.64 V vs. S                                         (3)

On the other hand in the cathode side if H₂O₂ is an oxidant

The electrochemical decomposition of H₂O₂ as

4H₂O₂ + 8H⁺ + 8e⁻ --> 8H₂O, E° = 1.776 V

Depending on the pH of H₂O₂ solution in the catholyte with the cell potential ranging between 1.64 and 3.02 V.

The operating temperature is between 30 and 90 °C. The maximum power density of the DBFC obtained is about 0.68 Wcm^-2 at 60 °C with the use of H₂O₂ as oxidant with high surface area (2000 m²/g) substrate.

Important advantages of DBFC

      High energy density
      High energy conversion efficiency
      High open cell voltage
      Non platinum catalyst
      Can be operated at room temperature
      Very fast start up time
      Fuel can be recycled