<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">\chapter{Introduction}
\label{cap:Introduction}

\section{Motivation}

As stated in the special report from the Intergovernmental Panel on Climate Change (IPPC), human activities have caused a increase in global temperatures of approximately 1.0 °C when compared to pre-industrial levels. Furthermore, this increase could reach up to 1.5 °C overall by the years 2030 or 2052 \citep{01_ipcc_sr15_2018}. The Paris Agreement aims to restrict the rise in global average warming to below 2 °C. To clarify the varying degrees of risk, global average warming can be divided into three categories: &gt;1,5°C, classified as dangerous, &gt;3°C, deemed catastrophic, and warming exceeding 5°C, classified as "unknown", suggesting that it is beyond this rise in temperature that an existential threat by the year 2050 is possible \citep{01_xu_ramanathan_2017}.

The new climate protection program released by the German government on the 17 of July, 2024 has set the goal of cutting greenhouse gas emissions (GHG) by 65\% relative to 1990 levels by the year 2030. Additionally, it sets a target for Germany to achieving greenhouse gas neutrality by 2045 \citep{01_E_klimaschutzgesetz}.

When looking into different GHG emissions, it is of note that 80,6\% may be attributed to CO$_2$. Meanwhile, methane (CH$_4$), as well as nitrous oxide (N$_2$O), are responsible for 12,1\% and 5,3\% \citep{01_umweltbundesamt_treibhausgas_eu}. 
It is estimated that anthropogenic GHG emissions have contributed to the rise of global average temperature by 0,8 to 1,3 °C from 1850-1900 to 2010-2019. For the estimate of 1,3°C, CO$_2$ alone accounts for 0,85 °C \citep{01_ipcc_ar6_wg1_2021}.

Since the effect of CO$_2$ on global warming is undeniable, it is worth looking at this aspect of GHG more closely. In 2024, traffic in Germany amounted to 19,8\% of total GHG emissions. \citep{01_umweltbundesamt_verkehr_emissionen}. This percentage in the EU can be broken down by vehicle type: passenger cars and motorcycles were responsible for the largest proportion, contributing 60\% of the emissions, while buses and trucks accounted for 27\%. Light commercial vehicles contributed the smallest share at 13\%. Furthermore, traffic emissions have not only been increasing in Germany but also EU-wide, with an estimated 24\% rise in CO$_2$ since 1990 \citep{01_destatis_co2_strassenverkehr}. 

Since fossil fuels account for almost 90\% of all CO$_2$  emissions the importance of transitioning to renewable energy sources cannot be overstated \citep{01_un_climatechange_causes_2023}. Viable alternatives to internal combustion engines (ICEs) are on the rise, such as battery electric vehicles (BEVs) as well as hydrogen fuel cell vehicles (FCEVs). By adopting these greener alternatives, GHG emissions by the transportation sector could be significantly reduced, contributing to a more sustainable future \citep{01_wilberforce_advances_2016}.

When compared to the other alternatives, fuel cells require less mantainance than ICEs, and their operating temperature can be as low as 80 °C, not unlike ICEs' operating temperatures, which can reach over 2000 °C. They may also be recharged almost instantly, unlike BEVs \citep{01_wilberforce_advances_2016}. 
Although fuel cell technology is very promising and its development is advancing at a fast pace, there are still some challenges that make commercialisation difficult. One factor in particular is the cost of materials and components 
\citep{01_wilberforce_developments_2017}. 
The bipolar plate (BP) of a proton-exchange membrane fuel cell (PEMFC) accounts for 45\% of the stack manufacturing cost \citep{wang_preparation_2018}. 

Metals such as SS316L have been under investigation for some time to reduce material and production costs of bipolar plates and as such of a PEMFC \citep{wang_preparation_2018}. 
While stainless steel has some promising attributes such as good mechanical strength and high power density, it also has its downsides as they corrode metallic BPs. Another problem is membrane degradation, which could also be coupled with corrosion of BPs as the Fe$^{2+}$ ions released from the plate move to the membrane and intensify the degradation \citep{elferjani_coupling_2021}.




\section{Problem Statement}
E
In the past, bipolar plates for PEMFCs have been made out of titanium or Ti-C Coated materials. 
%Toyota quelle titan platten.
Since bipolar plates contribute to 45\% of stack costs, there has been a constant search for new materials that could also fulfill requirements at a lower cost \citep{wang_preparation_2018}. Even though the production of stainless steel plates would both cost just a fraction of titanium plates and have mechanical strength and conductivity meeting requirements, they are not as corrosion-resistant as titanium. As a result, stainless steel plates have been under investigation for some time. Methods employed thus far to evaluate the corrosion resistance and damage of PEMFCs have primarily focused on ex-situ analysis of materials, and rarely on in-situ methods, or even analysis of the actual bipolar plates with ex-situ methods. \\
%no good insitu methods...
\\The purpose of this master's thesis is presented as followed:
\begin{enumerate}
	\item To deepen the understanding of corrosion on stainless steel bipolar plates by analyzing SS316L plates and defining the main corrosion mechanism.
	\item To understanding which operating conditions will reinforce corrosion. 
	\item To develop a endurance run with reinforcing conditions for corrosion.
	\item To further development of ex-situ analytical methods to characterise, detect and evaluate corrosion damage on bipolar plates.
\end{enumerate}




\section{Outline of the Thesis}
In the last part of the introduction, the outline of your report should be defined. You should include the approach and applied strategy to solve your assignments as well.
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