The search for sustainable energy has shifted much research from proton exchange membrane fuel cells (PEMFCs) using a platinum catalyst to anion exchange membrane fuel cells (AEMFCs) with cheaper, more abundant metal catalyst alternatives. Prior research has already been conducted finding that nickel alloys are a strong catalyst for the oxygen reduction reaction. In our research, we continued investigating the efficiency of nickel alloy catalysts and tested two silver-nickel bimetallic nanoparticles, Ag3Ni and AgNi3. This work examines the change in power density of AEMFCs from two variables. First is the difference in size and mass of the bimetallic nanoparticles(NPs). Second is the application of the nanoparticles onto the anion exchange membrane with either a Point Zero Airbrush or a Langmuir-Blodgett Trough. Before testing, nanoparticles were synthesized using the Brust method in a 3:1 and 1:3 ratio. LB trough was used to graph the isothermal curves for both NPs and it was determined both NPs formed monolayers at around 2 mN. The control group consisted of an AEMFC with a 5 cm2 active area Sustainion membrane and 0.76 mg/cm2 platinum catalyst producing a maximum power density of 0.42 W/cm2. Sustainion membranes for each of the test variables were then prepared. A monolayer of Ag3Ni was deposited on both sides of a membrane with an LB trough at 2 mN of surface pressure. This process was repeated for AgNi3. Both AgNi3 and Ag3Ni outperformed the control group with maximum power densities of 0.51 W/cm2 and 0.58 W/cm2 respectively. Additionally, 3:1 ratio of Ag to Ni is the more efficient catalyst. For the sprayed NPs, the mass of nanoparticles was kept the same as with the LB trough. Airbrush was used to spray the NPs onto both sides of the membrane. Ag3Ni gave significantly higher results when the NPs were sprayed randomly compared to LB with maximum power densities of 0.71 W/cm2 and 0.58 W/cm2 respectively. Sprayed AgNi3 also gave higher results with a maximum power density of 0.53 W/cm2 compared to 0.51 W/cm2. A model designating these particles as simply augmenting the total amount of catalyst is not correct, since the spray or the LB particles added represent 45 micro-grams of catalyst relative to the amount already in the MEA. And for maximum, it provides a 69% power output increment. Hence synergistic reactions may also play a role in this system as well. Further experiments, as well as DFT simulations, are in progress to understand this phenomenon.

Enhancement of AEMFCs using bimetallic Ag3Ni and AgNi3 nanoparticles

ACS Spring 2022

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