Numerous diamond materials have been emerging as a critical material for various applications, due to their unique chemical, physical, and mechanical properties. Among them, conductive diamond films, in most cases doped diamond films (Dia) have been widely employed as electrodes for advanced electrochemical applications. Doping of diamond films refers to the introduction of foreign atoms such as boron, nitrogen, or phosphorus into the diamond lattice, leading to their altered electronic and structural characteristics. Of special interest, a co-doping process involves simultaneous incorporation of two or more dopants (e.g., boron and nitrogen), thus synergistically optimizing the diamond’s conductivity, electrochemical activity, and stability. These co-doped diamond films enhance charge transport, create additional active sites, and improve catalytic efficiency, enabling their broader applications in fields such as energy storage, pollutant degradation, and catalysis. Different from (co-)doped diamond films, diamond composites (DCs) - comprise diamond and other components, thus offering unique opportunities to further leverage these advancements. They effectively combine the outstanding properties of diamond with those of its components, leading to extensive exploration and testing in mechanical, physical, chemical, and biomedical applications. This "1+1 > 2" strategy has proven to be highly efficient for designing and developing advanced diamond-based functional materials. Although DCs offer exceptional chemical and physical properties, the poor electrocatalytic performance of diamond-based electrodes, mainly due to limited active sites, presents a significant challenge. In this context, this thesis addresses above issues by harnessing boron and nitrogen co-doped diamond (BNDD) composites, designing various interlayers and further adding surface modifications – the formation of DCs - to gain enhanced electrocatalytic activity and stability of these diamond materials, and exploring their electrochemical applicaitons in the fields of electrochemical energy storage (here supercapacitors and zinc batteries) and conversion (here electrocatalytic nitrate reduction reaction). This thesis firstly outlines the experimental techniques for synthesizing and characterizing these materials, including magnetron sputtering, electrodeposition, and microwave plasma-enhanced chemical vapor deposition. Its focus then shifts to the preparation and characterization of BDDD films and their composites, including BNDD/Metal/Si, Cu2O@CNF-BNDD (CNF = carbon nano fibers), and partially covered BNDD/Ti/Si. Detailed methods for analyzing the morphology, surface chemistry, and electrochemical performance of these films are discussed, along with their electrochemical applications such as supercapacitor formation, catalytic nitrate reduction and its integration with electrochemical methyl orange (MO) degradation using BNDD films, and Zn-nitrate batteries. The details of these contents are described as follows. In the first experimental system, the BNDD films were grown on a Si substrate with/without Ti and Ta interlayers, resulting in the fabrication of BNDD/Si, BNDD/Ti/Si, and BNDD/Ta/Ti/Si electrodes. After they were characterized using microscopies, spectroscopies, electrochemical techniques, and density functional theory (DFT) simulations, the relationship between their composition, interfacial structure, charge transport, and electrochemical properties was investigated. The BNDD/Ta/Ti/Si electrodes demonstrated faster electron transfer rates and lower resistances for redox probes compared to other diamond electrodes. The formation of TaC facilitated carrier tunneling and increased the concentration of electrically active defects, enhancing its electrochemical performance. As a case study, the BNDD/Ta/Ti/Si electrode was employed as a capacitor electrode to construct a redox-electrolyte-based supercapacitor. This section highlights the importance of interlayer composition and its impact on charge transfer and relevant electrochemical performance of co-doped diamond films, in other worlds how a tailored interlayer design can unlock new capabilities of co-doped diamond (e.g., BNDD) films. In the second experimental system, the BNDD surface was functionalized with carbon nanofibers (CNF) and further with Cu2O. The resultant Cu2O@CNF-BNDD composite was introduced as an efficient electrocatalyst for the electrochemical nitrate reduction reaction (NO3RR). This composite has unique properties of BNDD films, CNFs and Cu2O. For example, the BNDD films have a wider electrochemical potential window that suppresses the competing hydrogen evolution reaction (HER), resulting in a high NO3RR faraday efficiency. The CNFs grown on the BNDD surface regulate the sp2 content, enhancing electrical conductivity and electrochemical activity. Furthermore, the Cu2O catalyst donates electrons to the lowest unoccupied π* orbital of NO3-, making it highly effective for NO3RR. As revealed in DFT calculations, the d-band center of Cu 3d orbitals of reconstructed Cu NPs is shifted to −2.47 eV, balancing the adsorption of nitrogen-contained intermediates, and reducing the overpotential of NO3RR from 1.11 eV to 0.15 eV. Taking the advantage of a eight-electron nitrate-to-ammonia reaction and the exceptional activity of Cu2O@CNF-BNDD, a Zn-nitrate battery system was further proposed, where dual functionality was offered by using NO3RR-generated electrons for both electricity production and ammonia generation. This strategy simultaneously degrades nitrate pollutants and produces valuable chemicals. In the third experimental system, the sluggish oxygen evolution reaction (OER) was proposed to be replaced with a fast photo-electrocatalytic oxidation reaction of methyl orange (MO) with an aim to address the slow kinetics of the eight-electron NO3RR. In such an integrated system, the anodic MO degradation reaction occurring on a BNDD/Ti/Si electrode provides electrons, while the cathodic reaction performed on a Cu2O/CNF-BNDD cathode reduces nitrate to ammonia. Comprehensive characterization of these composite electrodes demonstrates their impact on electron transfer and electrochemically active surface area for both processes. This "three birds with one stone" strategy not only degrades nitrate pollutants and produces valuable chemicals, but also degrades dye molecules, providing a framework for viable NO3RR and waste degradation processes. In summary, this thesis provides new insights into the design and optimization of BNDD films and their composites for some potential electrochemical energy storage and conversion applications. By enhancing active sites and modifying surface structure of BNDD films, this thesis proves the great appeal of co-doped diamond films and their composite in the aspects of electrochemical energy storage, pollutant degradation, and electrocatalysis, boosting future developments in the synthesis, characterization and electrochemical applications of various diamond materials and related devices.

With the development of globalization, more and more students choose to study abroad, and issues related to the acculturation of international students have become increasingly prominent, affecting their academic performance, social life, mental health, values, and physical well-being. However, existing research lacks in-depth exploration of the intrinsic mechanisms of international students’ acculturation process from the view of international students themselves. This study adopts grounded theory and conducts in-depth interviews with six international students in Germany. Based on the data collected, their acculturation process is conceptualized as a "journey", and the analysis is organized into three stages: before the journey, focusing on their motivations; during the journey, detailing the acculturation process including emotional changes, challenges, and coping strategies; and after the journey, describing the transformations experienced by international students. The study finds that compared with the traditional assumptions of "integration" or "assimilation", contemporary international students are more inclined to selective acculturation and multicultural coexistence. And the international students’ acculturation reflects a new era feature with the development of technology, enlargement of globalization, and more convenience of the transportation, shifting from integration orientation to instrumental orientation and self-directed orientation. Based on these insights, this study proposes a theoretical model of international students’ acculturation: the "Difficulty-Coping" model, emphasizing that acculturation of international students is a phased process centered on problem solving, rather than a single assimilation path, which provides theoretical contributions and practical inspiration for better understanding the acculturation mechanism of contemporary international students.

In this dissertation, I examine processes of medicalization and psychologization in different discourses. Medicine and psychology have played a substantial role in describing social conditions, which is true in a variety of contexts. From sci- entific discourses, in which knowledge is generated and discussed to public dis- courses like mass media or political debates. A central concern of this disserta- tion is the mechanism by which such processes occur, and which actors are in- volved. For the scientific discourse, I analyzed which disciplines are leading in the international research on poverty in the Web of Science (WoS) between 1956-2017 and which changes in content are thus evident over time. In the (mass) media discourse based on different daily and weekly newspapers in Ger- many, I examined how the reporting of the last 25 years on unemployment and childhood is shaped and whether these two areas are more strongly linked to medical and psychological issues. In a further contribution, I focused on the COVID-19 pandemic. Since external influences may also cause medicalization and psychologization tendencies to emerge, I analyzed to what extent school closures in Germany have been a driver for an increased interest in mental health among children and adolescents. Here I was able to show that this was indeed the case and that, in addition to the purely epidemiological aspects of the pan- demic, threats to mental health as a side effect of the non-pharmaceutical measures became more prominent. Overall, I show that processes of medicalization and psychologization are traceable in various discourses through different actors and that external influ- ences like the COVID-19 pandemic can play a significant role.

In den 1990er-Jahren wurden in Peru bis zu 300.000 indigene, vorwiegend auf dem Land lebende Frauen im Rahmen einer Gesundheitsreform zwangssterilisiert. Seit fast dreißig Jahren gründen diese betroffenen Frauen Organisationen, um sich selbst zu organisieren. Ein zentrales Ziel dieser Selbsthilfeinitiativen ist es, die erlittene staatliche Gewalt sichtbar zu machen, ihre Folgen zu benennen und Entschädigungen zu fordern. Die vorliegende soziologische Studie beleuchtet die Erfahrungen dieser zivilgesellschaftlich engagierten Frauen in Peru, die sich seit drei Jahrzehnten für ein würdiges Gedenken und die Verantwortungsübernahme des Staates einsetzen. Aus einer dekolonialen und geschlechtertheoretischen Perspektive werden die vielschichtigen gesellschaftlichen Dynamiken beleuchtet, die zur staatlichen Gewalt führten und weiterhin fortwirken. Auf Grundlage empirisch-qualitativer Analysen macht die Studie einerseits deutlich, wie ungleiche Geschlechterverhältnisse, struktureller Rassismus und reproduktive staatliche Gewalt unter einem autoritären Regime zusammenwirken. Andererseits wird deutlich, dass eine aktive und vernetzte Zivilgesellschaft konstitutiv für eine demokratische Gesellschaft ist – ein innovativer Beitrag zu einem Thema von internationaler Relevanz, welches in Zeiten globaler politischer und gesellschaftlicher Herausforderungen von höchster Aktualität ist.