Au ₁ ‐N ₃ Site Induced Mid‐Band Charge Trapping in Carbon‐Defective Holey G‐C _3‐x N ₄ Enhances Highly Efficient Photocatalytic H ₂ Production

Abstract Gold (Au)‐involved water photocatalysis represents a promising approach for highly efficient solar‐to‐H 2 conversion due to the appropriate work functions for photoelectron separation and proton reduction. However, the scarcity and high cost of gold present significant challenges for industrial‐scale applications. The traditional Au nanocluster, as a co‐catalyst, shows suboptimal function‐to‐price ratios owing to the insufficient catalytic sites. Herein, a synergistic strategy of Au 1 ‐N 3 engineering (for maximum atomic sites exposure) and mid‐band assistance (for electron–hole separation) is developed to achieve tunable photodynamics and enhance photoactivity for g‐C 3 N 4 ‐based photocatalysis. The specially engineered coordination environment via porous and defective structure facilitates the formation of single‐atomic Au 1 ‐N 3 sites, consequently enabling a novel mid‐band induced the long‐lived excited state and a significant * H desorption enhancement for highly efficient proton–electron coupling. As a result, the H 2 production performance of bulky g‐C 3 N 4 is only slightly noticeable, and the Au single atoms coordinated holey g‐C 3‐x N 4 (Au 1 ‐Ho@g‐C 3‐x N 4 ) shows ≈333% increase in H 2 production (3.2 mmol h −1 g cat −1 or 157 mmol h −1 g Au −1 ) than that of Au nanocluster modified holey g‐C 3‐x N 4 (Au n ‐Ho@g‐C 3‐x N 4 ) (0.96 mmol h −1 g cat −1 ). Experimental and theoretical results reveal a prolonged lifetime of active photoelectron from ps to ns via Au 1 ‐N 3 induced mid‐band trapping process, which favors high charge mobility for electron‐involved H 2 generation.