A Tautomeric Carbon Nitride Structure for Photocatalytic Overall Water Splitting

Abstract

ABSTRACT Constructing type‐II heterojunctions is a prevalent strategy for enhancing the photocatalytic performance of polymeric carbon nitride (PCN). However, conventional PCN‐based type‐II heterojunctions are often limited by incoherent interfacial contacts, high charge‐transfer resistance, and poorly aligned energy levels with large band offsets, all of which impede interfacial charge transfer and degrade the redox capability of photocarriers. In this study, we report a pseudo‐resonance transformation strategy to selectively convert melon‐type carbon nitride (MCN) into a topologically analogous yet electronically distinct conjugated derivative (C─MCN). This process constructs a unique MCN/C─MCN tautomeric heterojunction​ featuring a chemically bonded, coherent, and dangling‐bond‐free interface. Carrier dynamics analysis reveals that this structural continuum significantly lowers the energy barrier for exciton dissociation while facilitating efficient interfacial charge transfer. As a result, the obtained tautomeric heterojunction exhibits outstanding photocatalytic overall water splitting performance, achieving a hydrogen evolution rate 2.3 and 2.6 times higher than that of pristine MCN and standalone C─MCN, respectively. This work establishes a new paradigm for fabricating dangling‐bond‐free polymeric heterojunctions, providing an efficient pathway toward solar‐fuel production.