Shahid Pottachola Shafi

A Direct Alcohol Fuel Cell Driven by an Outer Sphere Positive Electrode

Molecular oxygen, the conventional electron acceptor in fuel cells poses challenges specific to direct alcohol fuel cells (DAFCs). Due to the coupling of alcohol dehydrogenation with the scission of oxygen on the positive electrode during the alcohol crossover, the benchmark Pt-based air cathode experiences severe competition and depolarization losses. The necessity of heavy precious metal loading with domains for alcohol tolerance in the state of the art DAFC cathode is a direct consequence of this. Although efforts are dedicated to selectively cleave oxygen, the root of the problem being the inner sphere nature of either half-cell chemistry is often overlooked. Using an outer sphere electron acceptor that does not form a bond with the cathode during redox energy transformation, we effectively decoupled the interfacial chemistry from parasitic chemistry leading to a DAFC driven by alcohol passive carbon nanoparticles, with performance metrics ∼8 times higher than Pt-based DAFC-O2.

Fuel Exhaling Fuel Cell

State-of-the-art proton exchange membrane fuel cells (PEMFCs) anodically inhale H2 fuel and cathodically expel water molecules. We show an unprecedented fuel cell concept exhibiting cathodic fuel exhalation capability of anodically inhaled fuel, driven by the neutralization energy on decoupling the direct acid-base chemistry. The fuel exhaling fuel cell delivered a peak power density of 70 mW/cm2 at a peak current density of 160 mA/cm2 with a cathodic H2 output of ∼80 mL in 1 h. We illustrate that the energy benefits from the same fuel stream can at least be doubled by directing it through proposed neutralization electrochemical cell prior to PEMFC in a tandem configuration.

A vitamin C fuel cell with a non-bonded cathodic interface

Vitamin C is a naturally occurring molecule with antioxidant properties, and it often plays a pivotal role in many chemical and biochemical processes. We show that a cobalt-based molecular electrocatalyst can mediate the electron donation from vitamin C which upon coupling with a non-bonded and reversible electron acceptor; the electron flow between the half cells can be channeled in a precious-metal-free configuration. The non-bonded nature of the electron acceptor allows fast interfacial kinetics even on simple carbon particles and arrests the cathode-derived parasitic chemistry often encountered in oxygen breathing fuel cells. Consequently, a vitamin C fuel cell driven by the non-bonded cathodic interface demonstrates ∼18 times higher performance metrics compared to the precious-metal-based vitamin C–O2 configuration. Due to the renewable nature of the fuel and the precious metal-free configuration in the proposed non-bonded architecture, the cell can noticeably reduce the cost of electricity per kW with potential practical applications in powering commercial electrical appliances.