Unlocking the Potential of Carbon Nitride (C <i> _x </i> N <i> _y </i> ) Electrocatalysts in Hydrogen Evolution, Oxygen Evolution and Overall Water Splitting

Electrocatalytic water splitting with carbon nitride (C <i>_x</i> N <i>_y</i> ) materials has gained significant interest, driven by extensive research validating their synthesis, structure, and applications. Among various C <i>_x</i> N <i>_y</i> stoichiometric ratios, graphitic carbon nitride (g-C₃N₄) stands out as the most stable configuration and is extensively studied in the literature. However, other C <i>_x</i> N <i>_y</i> structures like g-CN, C₂N, C₃N₅, and C₉N₄ have been booming recently as well by exploration of their greatness. Recent progress of C <i>_x</i> N <i>_y</i> -based electrocatalysts in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting (OWS) has been examined meticulously. More emphasis has been placed on exploring the synthesis-structure-performance and simulate-structure-performance relationships of C <i>_x</i> N <i>_y</i> electrocatalysts in experimental and computational studies, respectively. This review outlines a clear framework for unifunctional C <i>_x</i> N <i>_y</i> electrocatalysts in HER and OER, focusing on recent advancements in (1) defect engineering, (2) structural engineering, and (3) hybridization. The research on bifunctional C <i>_x</i> N <i>_y</i> electrocatalysts is highlighted and explored through two main approaches: intrinsic and extrinsic modifications. Finally, the strategies and perspectives for creating novel highly efficient C <i>_x</i> N <i>_y</i> electrocatalysts for HER, OER, and OWS are analyzed. This review aims to inspire researchers to incorporate computational methods into experimental studies for developing highly efficient bifunctional C <i>_x</i> N <i>_y</i> -based electrocatalysts.