Graphitic carbon nitride (g-C₃N₄) has recently emerged as a promising metal-free photocatalytic material for the conversion of solar energy into chemical energy under visible-light irradiation. Unfortunately, the photocatalytic activity of g-C₃N₄ is still unsatisfactory due to the serious recombination of photogenerated electron–hole pairs. Here, we develop a strategy to construct a type of g-C₃N₄-based composite photocatalyst (C₃N₄/CBV²⁺), a g-C₃N₄ surface coupled with a viologen redox mediator (1,1′-bis(4-carboxylatobenzyl)-4,4′-bipyridinium dichloride, denoted as CBV²⁺) through hydrogen bonds, for enhanced H₂ production from water under visible-light irradiation. The CBV²⁺ molecules not only provide sites for metal particle formation but also act as an efficient electron transfer mediator to transfer the photoinduced electrons from g-C₃N₄ to platinum nanoparticles (Pt NPs). The vectorial charge transfer results in an efficient spatial separation of electrons and holes in the C₃N₄/CBV²⁺ composite photocatalyst and facilitates the photogenerated charge carriers for direct photocatalytic water splitting. When 1 wt % CBV²⁺ is introduced, the hydrogen production rate of C₃N₄/CBV²⁺ dramatically increases up to 41.57 μmol h^–1, exceeding 85 times the rate over unmodified g-C₃N₄ (only 0.49 μmol h^–1). It is noted that a negligible loss of photocatalytic activity was observed over continuous irradiation up to 20 h, demonstrating its good stability. The combination of the two emerging functional materials represents a simple but economical and powerful approach for highly effective photocatalytic hydrogen production under visible light irradiation. This study opens a window to rationally develop cost-acceptable materials for more efficient solar energy conversion applications.

中文翻译：

---

gC ₃ N _4结合氢的紫精显着增强了可见光光催化H _2的释放

石墨碳氮化物（gC ₃ N ₄）最近作为一种有前途的无金属光催化材料出现，用于在可见光照射下将太阳能转化为化学能。不幸的是，由于光生电子-空穴对的严重复合，gC ₃ N ₄的光催化活性仍然不能令人满意。在这里，我们开发一种策略来构建一种基于gC ₃ N ₄的复合光催化剂（C ₃ N ₄ / CBV ²⁺），一种gC ₃ N ₄表面通过氢键与大分子氧化还原介体（1,1'-双（4-羧甲基苄基）-4,4'-联吡啶二氯化物，表示为CBV ²⁺）偶联，以增强可见光照射下水中的H ₂产生。CBV ²⁺分子不仅提供了形成金属颗粒的位置，而且还充当了有效的电子转移介质，将光诱导的电子从gC ₃ N ₄转移到铂纳米颗粒（Pt NPs）。矢量电荷转移导致C ₃ N ₄ / CBV ²⁺中电子和空穴的有效空间分离复合光催化剂，并促进光生电荷载体直接进行光催化水分解。当引入1 wt％的CBV ^2+时，C ₃ N ₄ / CBV ²⁺的氢气产生速率急剧增加至41.57μmolh ^–1，是未改性gC ₃ N ₄的氢生成速率的85倍（仅0.49μmolh ^{– 1个}）。值得注意的是，在长达20小时的连续照射下，光催化活性的损失可忽略不计，表明其良好的稳定性。两种新兴功能材料的结合代表了一种在可见光照射下高效光催化制氢的简单但经济且功能强大的方法。这项研究为合理开发成本可接受的材料以实现更高效的太阳能转换应用打开了一个窗口。