Effective sulfur-doping enables remarkable photoelectrochemical performance of carbon nitride films in water splitting

AbstractPhotoelectrochemical (PEC) water splitting has been the most attractive route for solar hydrogen production, yet the development of efficient and metal-free photoanodes remains a critical challenge. Herein, we report a hetero-bond engineering strategy that breaks through the performance bottleneck of graphitic carbon nitride (g-CN) by introducing sulfur (S) into the tri-s-triazine framework. Through optimizing the precursor mass ratio of melamine-to-thiourea (3: 2) and calcination temperature (500 °C), we achieve the morphology control of ubiquitous g-CN micronflowers with improved film quality and polymerization degree. Under AM 1.5 G illumination, the photoanode reaches 790.5 μA cm−2 in 0.1 M Na₂SO₄ electrolyte with 10% triethanolamine (TEOA) at 1.23 V vs. RHE and a solar-to-hydrogen (STH) efficiency of 0.74 % under sacrificial agent (10% TEOA), outperforming most dual-precursor g–CN–based photoanodes. Mechanistic investigations reveal that the enhanced PEC performance is primarily attributed to the C–S–C bonds formed via S intercalation into N vacancies of g-CN, which play the role of photoactive centers in narrowing the bandgap and suppressing the charge carrier recombination. This work not only provides atomic-level insights into the electronic structure modulation of 2D polymeric semiconductors, but also establishes a generalizable precursor-design paradigm for fabricating high-performance, earth-abundant photoelectrodes. © 2026 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.