Introduction
This case study was conducted by a catalyst manufacturing
company to evaluate and validate Momentum Materials’ NCP Supports™ as a
catalyst support for hydrogen fuel cells. The study was completed in 2024.
Momentum Materials®: Tunable Nanoporous Carbon
Momentum Materials has developed NCP Supports™, an ordered nanoporous carbon material with tunable pore size and a 3D interconnected porous structure. Building on its experience in advanced carbon materials for electrochemical applications, Momentum Materials offers NCP Supports™ as a practical solution for high-performance and durable proton exchange membrane (PEM) fuel cells.
Scope and Objectives
This case study aimed to validate the performance and durability of Momentum Materials’ NCP-10-HT (10 nm pore size) as a catalyst support and assess its applicability in PEM fuel cells. The catalyst manufacturer synthesized a 60 wt.% Pt catalyst supported on NCP-10-HT, hereafter referred to as 60% Pt/NCP. Membrane electrode assemblies (MEA) were prepared using 60% Pt/NCP to assess its performance in PEM fuel cells.
Membrane Electrode Assembly
The membrane electrode assembly (MEA) has an effective area of 25 cm2. The catalyst is 60% Pt/NCP, with platinum loadings of 0.4 mgPt/cm2 on the cathode and 0.1 mgPt/cm2, on the anode. A proton exchange membrane with a thickness of 15 µm from Gore is used. Carbon paper of model H24CX 483 by Freudenberg is employed as the gas diffusion layer on both electrodes.
Key objectives included:
• Evaluating the electrochemical surface area (ECSA) and mass activity of 60% Pt/NCP.
• Assessing the performance of 60% Pt/NCP under varying humidity conditions, cell temperatures, and back pressures.
• Investigating performance degradation of 60% Pt/NCP under accelerated durability testing.
Results
Electrochemical Surface Area and Mass Activity
ECSA was measured in the MEA at low temperature using cyclic voltammetry (CV) (Figure 1) and calculated from the hydrogen underpotential desorption peak (Table 1). Mass activity was determined from the IR-corrected polarization curve collected with pure oxygen fed to the cathode, using the value at 0.9 V.
The ECSA and mass activity of 60% Pt/NCP are comparable to those of commercial 40% platinum on carbon black catalysts.
Figure 1 – Cyclic voltammetry response of 60% Pt/NCP in an MEA
Table 1 – ECSA and mass activity of 60% Pt/NCP
| Catalyst | ECSA (m2/gPt) | Mass Activity (A/mgPt) |
|---|---|---|
| 60% Pt/NCP | 52.78 | 0.1819 |
Effects of Humidity on the MEA Performance
Different OEMs have different system architectures. This leads to very different relative humidity requirements, so catalyst performance must be evaluated across a broad relative humidity window rather than at a single “optimal” condition.
The polarization curves were measured using a single fuel cell under the following conditions:
- Cell temperature: 75 °C
- Feed stoich: hydrogen/air – 1.5/2.5
- Absolute backpressure: 200 kPa
MEA composition is as described in scope and objectives.
Three different relative humidity (RH) conditions were tested: 55%, 80% and 100%, representing relatively dry, moderately hydrated, and humid environments. As shown in Figure 2, although performance decreases with reduced RH, the difference is not huge. At 0.65 V, the current density decreases by only 9.4% when RH is reduced from 100% to 55%. The difference is even smaller in the high current density region (Table 2).
Figure 2 – Polarization curves of the MEA at different relative humidity levels
Table 2 – Performance summary of the MEA under different relative humidity levels
| Humidity | Current density at 0.650 V | Voltage at 2 A/cm2 |
|---|---|---|
| 100% RH | 1.91 A/cm2 | 0.636 V |
| 80% RH | 1.84 A/cm2 | 0.623 V |
| 55% RH | 1.73 A/cm2 | 0.613 V |
High RH is beneficial for electrolyte hydration, leading to higher proton conductivity and improved performance in the activation region. Although high RH can increase the risk of flooding at high current densities, the 3D interconnected mesoporous network of NCP-10-HT, together with its hydrophobicity, facilitates efficient water removal.
Effects of Fuel Cell Temperature on the MEA Performance
Cell temperature is also a key parameter in system architecture design and varies among OEMs. Higher operating temperatures can improve power density but also pose challenges for material stability. Therefore, the MEA was evaluated at different cell temperatures to assess the flexibility of the 60% Pt/NCP catalyst under varied thermal conditions.
The polarization curves were measured under the following conditions:
- Relative humidity: 100%
- Feed stoich: hydrogen/air – 1.5/2.5
- Absolute backpressure: 200 kPa
MEA composition is as described in scope and objectives.
Three different cell temperatures were tested: 65°C, 75°C, and 85°C. As shown in Figure 3, cell performance at low overpotentials (activation region) is nearly identical. However, as current density increases beyond 1 A/cm2, the performance begins to diverge. Because higher temperatures increase water evaporation and improve mass transport, elevated cell temperature is beneficial for performance at high current densities (Table 3).
Figure 3 – Polarization curves of the MEA at different cell temperatures
Table 3 – Performance summary of the MEA under different cell temperatures
| Cell Temperature | Current density at 0.650 V | Voltage at 2 A/cm2 |
|---|---|---|
| 65℃ | 1.72 A/cm2 | 0.610 V |
| 75℃ | 1.90 A/cm2 | 0.633 V |
| 85℃ | 1.99 A/cm2 | 0.642 V |
Effects of Back Pressure on the MEA Performance
Back pressure is a key operating parameter in PEM fuel cells. Increasing back pressure raises reactant partial pressure, improving reaction kinetics and typically enhancing performance. However, high back pressure also increases system complexity and mechanical stress on cell components. As a result, some OEMs are pursuing ambient-pressure PEM fuel cells, which simplifies system design at the cost of peak power density. The MEA was therefore evaluated at different back pressures to assess the performance of the 60% Pt/NCP catalyst under varied back pressure conditions.
The polarization curves were measured under the following conditions:
- Cell temperature: 75°C
- Relative humidity: 100%
- Feed stoich: hydrogen/air – 1.5/2.5
MEA composition is as described in scope and objectives.
Three different absolute back pressure conditions were tested: 150 kPa, 200 kPa, and 250 kPa. As shown in Figure 4, increasing back pressure improves the fuel cell performance uniformly across the current density range. At 0.65 V, the current density increases by 14% when the back pressure is raised from 150 kPa to 250 kPa (Table 4). At 2 A/cm2, the overpotential decreases by 21 mV as the back pressure increases by 100 kPa (Table 4).
Figure 4 – Polarization curves of the MEA at different back pressure conditions
Table 4 – Performance summary of the MEA under different back pressure conditions
| Back Pressure (abs) | Current density at 0.650 V | Voltage at 2 A/cm2 |
|---|---|---|
| 150 kPa | 1.75 A/cm2 | 0.619 V |
| 200 kPa | 1.90 A/cm2 | 0.631 V |
| 250 kPa | 2.01 A/cm2 | 0.640 V |
Catalyst Durability
Catalyst durability is a critical factor in PEM fuel cells because it directly determines system lifetime and total cost of ownership. In this case study, the MEA was subjected to an accelerated catalyst test following the Department of Energy (DOE) protocol. The accelerated stressed testing conditions are as follows:
- Square wave cycles: steps between 0.6 V (3 s) and 0.95 V (3 s) with rise time of ~0.5 second or less. 30,000 cycles. Run polarization curve and ECSA at specified intervals.
The polarization curves were measured under the following conditions:
- Cell temperature: 75°C
- Relative humidity: 100%
- Feed stoich: hydrogen/air – 1.5/2.5
- Back pressure: 200 kPa
- Carbon paper compression: 20-25%
- Recovery follows DOE’s protocol
MEA composition is as described in scope and objectives.
Figure 5 – Catalyst durability evaluation of the MEA using the DOE protocol. (Left) Polarization curves and (right) cyclic voltammetry (anodic) of the fuel cell at the beginning of the test, after 10,000 cycles, and after 30,000 cycles.
As shown in Figure 5, the cell performance remains nearly unchanged after 30,000 catalyst durability cycles, demonstrating the strong durability of the 60% Pt/NCP catalyst under the fuel cell operating conditions. The calculated ECSA loss is 10.6%, while the performance loss at 0.8 A/cm2 is only 16 mV.
Carbon Durability
Under fuel cell operating conditions – especially during start-stop events – the carbon support can undergo electrochemical oxidation, weakening carbon-platinum interaction. This degradation promotes platinum degradation, leading to irreversible performance loss. As a result, selecting a durable carbon support is critical for overall catalyst lifetime. In this case study, the MEA was subjected to an accelerated carbon durability test following the DOE protocol. The accelerated stressed testing conditions are as follows:
- Triangle sweep cycle: 500 mV/s between 1.0 V and 1.5 V. 5,000 cycles. Run polarization curve and ECSA at specified intervals.
The polarization curves were measured under the following conditions:
- Cell temperature: 75°C
- Relative humidity: 100%
- Feed stoich: hydrogen/air – 1.5/2.5
- Back pressure: 200 kPa
- Carbon paper compression: 20-25%
- Recovery follows DOE’s protocol
MEA composition is as described in scope and objectives.
Figure 6 – Carbon durability evaluation of the MEA using the DOE protocol. (Left) Polarization curves and (right) electrochemical surface area changes of the fuel cell at the beginning of the test, and after 1000, 3000, and 5000 cycles.
As shown in Figure 6, cell performance below 1 A/cm2 remains nearly unchanged after 5000 carbon durability cycles, demonstrating well-retained catalyst activity even under harsh conditions. The apparent performance loss at higher current densities is likely due to the increased hydrophilicity of NCP-10-HT after carbon corrosion, which leads to higher water retention and increased oxygen transport resistance. The calculated ECSA loss is 35.1%, while the performance loss at 1.5 A/cm2 is 41.8 mV. This performance retention is significantly better than that reported for commercial Pt on carbon black catalysts.
Because NCP-10-HT undergoes high-temperature treatment, its increased graphitization level substantially enhances carbon corrosion resistance. The strong performance retention at low current densities further suggests that most Pt nanoparticles are deposited within the 10 nm mesopores and remain well protected, even under harsh durability testing conditions (1.0-1.5V).
Conclusions
This case study demonstrates that NCP-10-HT significantly improves catalyst durability while maintaining strong performance across a range of operating conditions.