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Energy and electricity are vital to modern society and our daily life. However, environmental pollution and global warming caused by fossil fuels have also become highly problematic in recent years. Hydrogen has the highest energy density, it can be produced directly from water, and the only by-product during the power generation is water. Therefore, hydrogen is considered to be the key to solving the current energy problem. However, the current mainstream hydrogen production methods also result in significant carbon emissions. In the meantime, the chemical reactions performed in water electrolysis and fuel cells rely heavily on expensive noble metal catalysts. Consequently, there is an urgent need to develop cheap and efficient catalysts to replace noble metals. Since 2009, nitrogen-doped carbon nanotubes have been proved to have a similar catalytic activity to platinum for oxygen reduction reactions (ORR) and better stability. Heteroatom-doped carbon materials have been developed rapidly over recent years and are now considered a promising alternative to noble metal catalysts. In addition to ORR, carbon materials can also catalyze hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with comparable performance to the commercialized noble metal catalysts while being cheaper to produce and more stable. This dissertation will be divided into several sections to discuss the application of functionalized carbon materials in various energy conversion and storage devices. Chapter 2 explore the potential application of functionalized graphene in the transport layer and active material for perovskite solar cells. Chapter 3 introduces a small project which combines perovskite material with electrospun fiber into a flexible photodetector. Chapters 4 and 5 investigate the multifunctional catalytic performance of nitrogen and sulfur co-doped 3D graphite networks (N, S-3DPG) in water splitting, fuel cells, dye-sensitized solar cells, and zinc-air batteries; we successfully used these low-cost carbon-based devices to build zero-emission clean hydrogen energy system that requires only sunlight and water to generate hydrogen and electricity. In the last part, we use inexpensive basic carbon materials to prepare large-area load-bearing supercapacitors with potential applications in flexible wearable devices.