Hydrogen represents a clean and sustainable energy carrier and a viable alternative to fossil fuels in transportation. Electrochemical water splitting is a particularly promising method for producing high-purity hydrogen from renewable sources, offering a pathway to mitigate both environmental pollution and the global energy crisis. The efficiency of this technology hinges on the performance of electrocatalysts, which lower the reaction barriers for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, designing electrocatalysts that are both highly active and durable remains a formidable challenge, necessitating precise control over their structure and electronic properties. Due to the abundance and affordability, carbon-based nanomaterials are exceptional candidates for this role, owing to their superior electrical conductivity, tunable physicochemical characteristics, and the possibility to introduce active sites. This review comprehensively examines the fundamental mechanisms of HER and OER and elucidates the pivotal function of electrocatalysts. We systematically discuss the properties, advantages, and synthesis of diverse carbon nanostructures, including zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) architectures. Furthermore, we explore advanced nanocomposites derived from carbon-containing platforms, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), porous organic polymers (POPs), and MXenes. The efficacy of these carbon-based catalysts for HER and OER is critically evaluated, alongside an analysis of the persistent challenges regarding their stability, efficiency, and scalability. Finally, we present a forward-looking perspective on the remaining challenges and future research directions in the field of carbon-based electrocatalysts for sustainable hydrogen production. Graphical ab

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