Unique nitrogen-deficient carbon nitride homojunction prepared by a facile inserting-removing strategy as an efficient photocatalyst for visible light-driven hydrogen evolution.

• Unique N-deficient g-C 3 N 4 homojunction was prepared by inserting-removing strategy. • 3-amino-1,2,4-triazol prepolymerization under optimized conditions is essential. • 3882.5 μmol h−1 g-1 high H 2 evoluation rate with 8.6 % AQY at 420 nm was obtained. • It comes from improved charge mobility, light absorption, and reduction potential. • It paves a new avenue for designing other efficient carbon nitride photocatalysts. Efficiently improving photocatalytic efficiency of carbon nitride (g-C 3 N 4), a promising candidate, for H 2 production is of great significance but remains a challenge. Herein, a unique N-deficient g-C 3 N 4 homojunction (I/R-CN) prepared by an inserting-removing strategy via thermal polymerization of a freeze-dried mixture containing dicyandiamide, NH 4 Cl, and a prepolymer from 3-amino-1,2,4-triazol (3-AT) is reported, in which the prepolymerization process of 3-AT under optimized conditions is indispensible. I/R-CN features the N-deficient g-C 3 N 4 microdomains (NDMD) from prepolymer inserting into a porous N-defects modified g-C 3 N 4 with two kinds of N defects (N vacancies and cyano groups) formed by removing N atoms from the skeleton of g-C 3 N 4 , unambiguously confirmed by various characterizations. I/R-CN exhibits notably promoted photocatalysis with a high H 2 evolution rate of 3882.5 μmol h−1 g−1 and a large apparent quantum yield of 8.6 % at 420 nm, originating from the efficient recombination inhibition of electron-hole pairs by the markedly promoted charge mobility as well as the improved light absorption capacity and enlarged reduction potential. This work paves a new avenue for designing other highly-efficient carbon nitride photocatalysts for solar applications. [ABSTRACT FROM AUTHOR]