Research Status of Platinum-Based Catalysts for Hydrogen Fuel Cells

Xin Wang

Material Science and Engineering School, Guangdong University of Petrochemical Technology, Maoming, 52500, China

Keywords: Hydrogen Fuel Cell, Platinum-Based Catalysts, Catalyst Carrier.

Abstract: The global focus has shifted towards new energy sources in recent years. With the increasing severity of

environmental pollution and climate change, countries and enterprises are seeking sustainable energy

solutions. Hydrogen fuel cell technology has emerged as a promising clean energy alternative, offering

significant potential in reducing carbon emissions and improving energy conversion efficiency. This

technology has garnered attention for its environmentally friendly characteristics and long-term energy

strategy implications, attracting the interest of scientists and engineers. Among the technical aspects of

hydrogen fuel cells, the role of platinum-based catalysts is particularly crucial. This paper provides an

overview of the most recent research advancements in the composition, structure, and carrier of platinum-

based catalysts used in hydrogen fuel cells. It delves into methods for enhancing the anti-poisoning

capabilities and stability of catalysts through doping and surface structure control. Additionally, it discusses

approaches to enhance carbon carriers by regulating the level of graphitization and oxidation.

1 INTRODUCTION

The global focus on energy issues has increased

significantly in recent years. With economic

development and population growth, the demand for

energy has risen rapidly. It is predicted that global

energy demand will continue to increase, reaching 23

TW in 2030 and potentially 30 TW in 2050. The

reliance on non-renewable energy sources like coal

and oil has led to environmental pollution, the

greenhouse effect, and resource depletion. In 2016,

renewable energy sources such as wind power,

biomass, and solar photovoltaic power accounted for

only 20.5% of global energy consumption. This

heavy reliance on fossil fuels has caused

environmental problems and contributed to global

warming. Therefore, there is a critical need to

prioritize research and application of renewable

energy for sustainable development (Zhu et al.,

2019).

Hydrogen energy, characterized by being zero-

carbon, pollution-free, renewable, high in energy

density, and diverse in acquisition methods, is

considered a promising alternative to traditional fossil

energy sources. Clean, renewable, and efficient

hydrogen power generation technology is seen as the

key to achieving a hydrogen economy. Hydrogen fuel

cells, known for their high efficiency, cleanliness, and

sustainability, are considered an ideal energy

conversion method without pollution and carbon

emissions. The only byproduct of hydrogen fuel cells

is water, and they do not involve the Carnot cycle,

resulting in high energy conversion efficiency.

Therefore, the development of catalysts with high

activity, stability, durability, and low cost has become

a focus of hydrogen fuel cell research (Wei et al.,

2019).

Platinum (Pt) catalysts are widely recognized as

efficient electrocatalysts for the hydrogen oxidation

reaction (HOR). They exhibit fast reaction rates,

particularly in acidic conditions, where the kinetics

are extremely rapid, with an exchange current density

of about 10

mA/cm²Pt. (Durst et al., 2014) Despite

their excellent performance, Pt catalysts have

drawbacks such as high cost, scarcity, susceptibility

to impurities, and unsatisfactory surface structure and

composition of catalyst carriers. These factors can

reduce catalyst activity, significantly impacting the

efficiency of hydrogen fuel cells in practical

applications. Therefore, current research on Pt-based

catalysts for hydrogen fuel cells primarily focuses on

regulating the composition and structure of the

catalyst particles and improving the catalyst carriers.

This article provides a summary of the current

research progress on Pt-based catalysts for hydrogen

fuel cells in terms of composition, structure, and

carriers, and proposes future research directions for

hydrogen fuel cell catalysts.

204

Wang, X.

Research Status of Platinum-Based Catalysts for Hydrogen Fuel Cells.

DOI: 10.5220/0013875400004914

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 2nd International Conference on Renewable Energy and Ecosystem (ICREE 2024), pages 204-208

ISBN: 978-989-758-776-4

2 CATALYST PARTICLES

In hydrogen fuel cells, the primary goal of

continuously optimizing catalyst particles is to

enhance catalytic activity, reduce costs, improve

durability and anti-poisoning performance, and

optimize the catalytic reaction path and mass transfer

efficiency. By introducing different elements, the

electronic structure and chemical properties can be

adjusted to enhance its anti-poisoning ability and

stability. Surface regulation technology optimizes

particle size, shape, and distribution, increases active

sites, and improves the adsorption and mass transfer

behavior of reactants. This helps in reducing the

amount of precious metals while maintaining high

performance, leading to economical and efficient

catalyst design. In the application process of platinum

catalysts, the negative hydrogen effect generated at

the anode can lead to catalyst poisoning, which is a

challenging issue to completely avoid in practical

applications. In hydrogen fuel cells, the negative

hydrogen effect refers to the presence of toxic gases

such as carbon monoxide (CO) and hydrogen sulfide

S) on the anode. These toxic gases will adsorb on

the surface of the platinum catalyst, hinder the

hydrogen oxidation reaction, reduce active sites, and

subsequently decrease the rate of hydrogen oxidation

reaction, thus affecting battery performance.

Therefore, current research focuses on solving the

problem of catalyst poisoning by optimizing catalyst

particles (Wang et al., 2020).

2.1 Transition Metal and Oxide Doping

Doping serves as an effective strategy for mitigating

platinum-based catalyst poisoning. By introducing

small quantities of other elements or compounds to

the catalyst, its catalytic performance can be fine-

tuned. This approach is widely employed in the

modified synthesis of platinum-based catalysts. The

introduction of new elements or components

generates electronic or bifunctional effects, allowing

for the optimization of the proportion, type, and

content of doping elements to maximize the catalyst's

resistance to CO poisoning (Zhang et al., 2021).

Incorporating oxygen-philic metal elements such

as ruthenium (Ru), iron (Fe), cobalt (Co), and nickel

(Ni) into platinum-based catalysts can enhance the

adsorption of surface hydroxyl groups (OH) through

bifunctional effects. This promotes the desorption of

CO oxidation to carbon dioxide (CO2) and improves

the CO tolerance and hydrogen oxidation reaction

activity of platinum-based catalysts. Notably,

platinum-ruthenium alloy catalysts have garnered

attention due to their exceptional resistance to CO

poisoning. The synergistic effect between platinum

and ruthenium reduces the oxidation potential of CO,

making it easier to be oxidized under low potential

conditions. Consequently, platinum-ruthenium alloy

catalysts generally exhibit superior CO tolerance.

Currently, PtRu catalysts are the most widely studied

and applied in the field of anti-CO poisoning. The

synergistic effect between Pt and Ru can reduce the

CO oxidation potential, making it easier to be

oxidized at low potentials. Therefore, PtRu catalysts

usually have better CO tolerance. Studies have shown

that the higher CO poisoning resistance of PtRu/C

catalysts comes from the oxidation and removal of

CO adsorbed on its surface, including direct

electrochemical oxidation and water-gas shift

reaction.

The water-gas shift reaction usually occurs at

180°C~350°C, so during the operation of the fuel cell,

the oxidation of CO on the catalyst surface is usually

dominated by electrochemical oxidation. For other

element doping, the high tolerance of CO is not only

due to the electrochemical oxidation process of

surface CO, but also the process of Mo catalyzing CO

and H

O in the water-gas shift reaction further

improves its anti-CO poisoning performance.

Therefore, the catalyst also has ideal HOR catalytic

activity in H

/CO (100 μmol/mol), and the cell

voltage only drops by 100 mV at a current density of

1 A/cm

, which is about 0.4 times that of the Pt/C

catalyst (Min, Kim and Jung, 2019).

To enhance the anti-CO poisoning performance of

Pt-based catalysts, it is vital to utilize the electronic

and bifunctional effects through doping. This

enhancement relies on the reasonable regulation of

several key factors, including the proportion, number,

and type of doping elements. Traditional alloys are

typically limited to combinations of two or three

elements. In contrast, high-entropy alloys, a new type

of alloy composed of no fewer than five metals, have

emerged in recent years. High-entropy alloys offer

high entropy effects, hysteresis diffusion effects,

lattice distortion effects, and cocktail effects,

allowing for the adjustment of metal components to

achieve improved stability and catalytic activity

compared to traditional alloys.

2.2 Surface Structure Control

Doping strategies have limitations in optimizing the

anti-poisoning performance of catalysts. Regulating

the surface structure of Pt-based catalysts offers a

new way to improve their performance further.

Different surface structures of crystals at the

Research Status of Platinum-Based Catalysts for Hydrogen Fuel Cells

205

microscopic level affect the adsorption characteristics

of CO on the catalyst surface. At the macroscopic

level, core-shell catalysts are a common means of

surface structure regulation. These catalysts consist of

a single or multi-layer Pt shell layer that plays a

catalytic role and a supporting core structure. By

adjusting the core type, surface Pt atomic coverage,

or the number of Pt shell layers, the center position of

the surface metal d band can be changed, thus

affecting the HOR activity and anti-poisoning ability

of the core-shell catalyst (Liang et al., 2020).

When the coverage of the Pt monolayer on the

surface of the catalyst core is less than 1, it acts as a

sub-monolayer core-shell catalyst. A low Pt coverage

results in a lower CO adhesion coefficient, and the

surface structure will affect the gas adsorption on the

metal surface, thus influencing the catalytic reaction.

Making reasonable changes in the coverage can

reduce the CO adsorption energy and improve the

anti-poisoning ability of the Pt-based catalyst.

Controlling the number of Pt shell layers has a

significant impact on the activity in the hydrogen

oxidation reaction (HOR) and the tolerance to carbon

monoxide (CO). Recent experiments demonstrated

that synthesizing two layers of Pt AL on PtCo/C

resulted in the formation of a Pt

2AL

-PtCo/C catalyst.

This catalyst was then tested using reformed

hydrogen as the experimental gas to assess its

durability. The findings indicate that the presence of

the Pt double layer prevents the core Co atoms from

corroding, leading to significantly improved stability.

Additionally, the CO adsorption on the Pt

2AL

-PtCo/C

catalyst is reduced, resulting in enhanced area

specific activity and durability of the catalyst in CO-

rich environments (Wang et al., 2018).

In addition to the core-shell structure, controlling

the special surface morphology of materials is also a

feasible method for surface structure control. By

enhancing the electronic structure characteristics of

bulk materials, more surface active sites are exposed,

leading to improved performance of anti-poisoning

catalysts. For instance, the synthesized three-

dimensional network structure of PtBi nanorod

catalyst enhances the utilization rate of Pt. Its

interconnected pore structure increases the overall

electrochemical active area of the catalyst.

Additionally, the bimetallic structure introduces an

oxygen-philic effect, which improves the CO

tolerance of the PtBi nanorod catalyst.

3 CATALYST CARRIER

Platinum-based carbon catalysts (Pt/C catalysts) are

commonly used as cathodic and anodic catalysts in

hydrogen fuel cells. However, they are often

negatively affected by harsh working environments,

leading to degradation and loss of activity. The

surface structure and composition of the carbon

carrier play a crucial role in the electrocatalytic

deactivation of these catalysts. An ideal carbon

carrier should possess good electron conductivity, a

reasonable pore structure, a large specific surface

area, and excellent resistance to electrochemical

corrosion. In traditional Pt/C catalysts, platinum

nanoparticles (PtNPs) have a high specific surface

energy, but their weak interaction with the carbon

carrier makes them prone to migration and

agglomeration. Furthermore, the surface of the

carbon carrier contains a large number of defects and

unsaturated bonds, rendering it susceptible to

oxidative corrosion under long-term working

conditions. This can result in the deterioration of the

carrier and the shedding of Pt NPs, ultimately

reducing the activity of the catalyst and leading to

deactivation. To address these issues, researchers

have modified the carbon carrier to effectively

prevent its corrosion and enhance the interaction

between Pt NPs and the carrier, thereby improving the

performance and durability of the catalyst.

3.1 Graphitization of Carbon Catalysts

The graphitization degree of carbon carriers has a

significant effect on its electrochemical corrosion

performance. By increasing the graphitization degree,

its anti-electrochemical corrosion ability can be

effectively enhanced, thereby avoiding the structural

collapse of the catalyst caused by carrier corrosion

during long-term operation. Recent studies have

shown that by precisely controlling the time and

energy distribution of laser irradiation of ethylene,

scientists have successfully synthesized a new type of

laser-induced carbon material, called onion-like

carbon (OLC). Raman spectroscopy characterization

results confirmed that OLC has a significant degree

of graphitization. In practical applications, Pt/OLC

catalysts show higher catalytic activity than

traditional Pt/C catalysts.

Compared with commercial carbon black (XC),

OLC has a unique concentric graphite layer structure

and σ-π bond hybrid structure, which significantly

enhances its interaction with platinum (Pt) atoms.

Such structural characteristics not only help to inhibit

the surface migration of Pt atoms, thereby improving

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the durability of the catalyst under long-term working

conditions, but also make OLC more stable in

electrochemical reactions. In addition, the d-band

center position of Pt on the OLC shell structure moves

downward. This change in electronic structure

reduces the adsorption strength of oxygen on the Pt

surface, thereby enhancing the activity of oxygen

reduction reaction (ORR). This shows that OLC has

significant advantages in improving catalyst

performance and durability, and provides new ideas

and methods for the development of high-

performance electrocatalysts (Muhyuddin et al.,

2023).

3.2 Carbon Carriers Oxidation

The oxidation treatment method effectively alters the

surface properties of the carbon carrier, promoting

interaction between the surface groups and platinum

nanoparticles (PtNPs). This treatment improves PtNP

dispersion and resolves migration and aggregation

issues during the catalytic process. Infrared

spectroscopy (IR) characterization reveals that

abundant functional groups are introduced on the

carbon black surface after oxidation treatment,

enhancing interaction with PtNPs and improving

catalyst performance.

Transmission electron microscopy (TEM)

characterization results show that carbon black

treated with different oxidation methods has varying

dispersion effects on PtNPs. H₂O₂ treatment

demonstrates the best PtNP dispersion, followed by

HNO₃ treatment, while untreated carbon black

exhibits the worst dispersion. This indicates that H₂O₂

treatment is more effective in introducing functional

groups, thereby improving PtNP distribution (Xia et

al., 2021).

Electrochemical tests demonstrate that oxidation

treatment significantly enhances the electrochemical

stability of Pt/C catalysts. TEM analysis before and

after durability cycling reveals that the average

particle size of PtNPs on untreated and treated carbon

supports increases from 2.5nm and 2.6nm to 5.3nm

and 4.8nm, respectively. These results show that

oxygen-containing functional groups introduced by

oxidation treatment help connect with metal

nanoparticles through oxygen atoms, reducing

nanocatalyst agglomeration.

In summary, oxidation treatment notably

improves PtNP dispersibility and reduces migration

and aggregation by introducing oxygen-containing

functional groups on the carbon support surface,

which significantly enhances the catalytic activity

and stability of the catalyst. This treatment method

offers an effective approach to developing efficient

and stable electrocatalysts.

3.3 Compound Doping Modification

The addition of semiconductor oxides, can

significantly enhance the electrochemical corrosion

resistance of the carrier and the overall performance

of the fuel cell. To prove this, the researchers mixed

carbon black XC-72 with anatase, loaded TiO

onto

the surface of the carbon black through hydrolysis,

and obtained a carbon powder (TiO

-C) containing 5

wt% TiO

after drying. They then used

photodeposition to deposit platinum nanoparticles (Pt

NPs) on the TiO

-modified carbon carrier to create

the Pt/TiO

-C catalyst.

Photodeposition is crucial in this process as it

facilitates the efficient deposition of Pt. This is

because under light conditions, the electron-hole pairs

generated on the oxide surface can reduce the noble

metal anions, resulting in more even distribution of

the Pt NPs on the oxide sites. Electrochemical test

results indicate that, compared to commercial Pt/C

samples, Pt/TiO

-C catalysts demonstrated superior

thermal stability and electrochemical activity at

different temperature ranges (298-343K).

Further fuel cell performance tests revealed that

the power density of Pt/TiO

-C catalysts increased

with rising temperature. This effect is primarily due

to the fact that the doping of TiO2 modifies the

surface activation energy of the catalyst, changes the

interaction between Pt NPs and the carbon carriers,

and thus generates a synergistic effect. These findings

demonstrate that the performance of Pt-based

catalysts can be effectively enhanced by doping TiO

in carbon carriers, offering a viable approach for

advancing fuel cell technology (Mobarakeh, 2017).

4 CONCLUSION

This article reviews the the latest research on

platinum-based catalysts for hydrogen fuel cells. It

focuses on the impact of catalyst particles, doping

technology, and carrier modification on improving

catalyst performance.

Firstly, by introducing transition metals and oxide

doping, the catalyst's resistance to carbon monoxide

(CO) poisoning and stability can be significantly

improved. This method adjusts the electronic

structure and surface chemical properties of the

catalyst, allowing it to operate efficiently while

reducing the amount of precious metals needed, thus

achieving an economical and efficient design.

Research Status of Platinum-Based Catalysts for Hydrogen Fuel Cells

207

Secondly, controlling the surface structure,

particularly the regulation of core-shell structures and

special surface morphology, is crucial for enhancing

the activity and durability of the catalyst. Core-shell

structures can optimize the hydrogen oxidation

reaction (HOR) activity and anti-poisoning ability by

adjusting the core type, surface platinum atom

coverage, or the number of shell layers, thereby

changing the surface metal d-band center position.

Special surface morphologies improve catalytic

reaction efficiency by increasing active sites and

enhancing gas adsorption characteristics on the metal

surface.

Furthermore, studies on carrier modification have

shown that increasing the degree of graphitization of

carbon carriers and introducing oxidation treatment

can significantly enhance the catalyst's resistance to

electrochemical corrosion and overall performance.

Graphitized carbon carriers offer better electronic

conductivity and structural stability, helping to

maintain the catalyst's structural integrity and high

performance during long-term operation. Oxidation

treatment, by introducing oxygen-containing

functional groups on the carbon carrier surface,

enhances the interaction between the carrier and

platinum nanoparticles (Pt NPs), reducing issues

related to nanoparticle migration and aggregation.

Lastly, doping the catalyst with semiconductor oxides

such as TiO

can enhance its thermal stability and

electrochemical activity. This method modifies the

catalyst's surface activation energy, improves the

interaction between Pt NPs and the carrier. As a

result, it increases the power density and the overall

performance of the fuel cell.

In conclusion, future research should continue to

focus on exploring new materials and methods to

improve the performance and durability of hydrogen

fuel cell catalysts. This will provide a solid scientific

foundation for the development of hydrogen energy

technology, promoting the widespread adoption of

clean energy and sustainable development.

REFERENCES

Zhu J, Lee L Y S, Hu L, Zhao P and Wong Y, 2019. Recent

Advances in Electrocatalytic Hydrogen Evolution

Using Nanoparticles

Wei C, Rao R R, Peng J, Huang B, Stephens I E L, Risch

M, Xu Z J and Shao‐Horn Y 2019 Recommended

Practices and Benchmark Activity for Hydrogen and

Oxygen Electrocatalysis in Water Splitting and Fuel

Cells Adv. Mater. 31 1806296

Durst J, Siebel A, Simon C, Hasché F, Herranz J and

Gasteiger H A 2014 New insights into the

electrochemical hydrogen oxidation and evolution

reaction mechanism Energy Env. Sci 7 2255– 60

Wang Y, Ruiz Diaz D F, Chen K S, Wang Z and Adroher

X C 2020 Materials, technological status, and

fundamentals of PEM fuel cells – A review Mater.

Today 32 178–203

Zhang J, Qu X, Shen L, Li G, Zhang T, Zheng J, Ji L, Yan

W, Han Y, Cheng X, Jiang Y and Sun S 2021

Engineering the Near‐Surface of PtRu

Nanoparticles

to Improve Hydrogen Oxidation Activity in Alkaline

Electrolyte Small 17 2006698

Min, Jeffery, Kim, and Jung 2019 Electrochemical Analysis

for Demonstrating CO Tolerance of Catalysts in

Polymer Electrolyte Membrane Fuel Cells

Nanomaterials 9 1425

Liang Z, Song L, Elnabawy A O, Marinkovic N,

Mavrikakis M and Adzic R R 2020 Platinum and

Palladium Monolayer Electrocatalysts for Formic

Acid Oxidation Top. Catal. 63 742–9

Wang T, Chen Z-X, Yu S, Sheng T, Ma H-B, Chen L-N,

Rauf M, Xia H-P, Zhou Z-Y and Sun S-

G 2018 Constructing canopy-shaped molecular

architectures to create local Pt surface sites with high

tolerance to H

S and CO for hydrogen

electrooxidation Energy Environ. Sci. 11 166–71

Muhyuddin M, Tseberlidis G, Acciarri M, Lori O,

D’Arienzo M, Cavallini M, Atanassov P,

Elbaz L, Lavacchi A and Santoro C 2023

Molybdenum disulfide as hydrogen evolution

catalyst: From atomistic to materials structure and

electrocatalytic performance J. Energy Chem. 87 256–

Xia C, Qiu Y, Xia Y, Zhu P, King G, Zhang X, Wu Z, Kim

J Y, Cullen D A, Zheng D, Li P, Shakouri M,

Heredia E, Cui P, Alshareef H N, Hu Y and Wang H

2021 General synthesis of single-atom catalysts with

high metal loading using graphene quantum dots Nat.

Chem. 13 887–94

Mobarakeh M D 2017 Synthesis of electrospun carbon

nanofiber/WO3 supported Pt, Pt/Pd and Pt/Ru

catalysts for fuel cells Fibers Polym. 18 95–101

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