In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for photoelectrochemical (PEC) applications, the fabrication of highly stable and photoactive PCN photoelectrodes has been a largely elusive goal to date. Here we tackle this challenge by devising, for the first time, a sol–gel approach that enables facile preparation of photoanodes based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol–gel process capitalizes on the use of a water-soluble PHI precursor composed of nanosized (~10 nm) particles that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on a conductive substrate resulting in formation of mechanically stable porous polymeric thin layers (~400 nm), in contrast to the commonly obtained loosely attached thick particulate coatings. The resulting photoanodes exhibit unprecedented PEC performance in methanol reforming in neutral pH electrolytes with very high photocurrents of 177±27 mA (1 sun illumination) cm-2 and 320±40 mA cm-2 (2 sun illumination) at 1.23 V vs. RHE, with very high photocurrents down to ~0 V vs. RHE. These parameters permit effective operation even without any external electric bias, as demonstrated by zero-bias photoreforming of methanol and glycerol, and highly selective (~100%) photooxidation of 4-methoxybenzyl alcohol (4-MBA). The robust binder-free films derived from sol–gel processing of water-soluble PCN thus represent a new paradigm for high-performance ‘soft-matter’ photoelectrocatalytic systems based on PCN.

中文翻译：

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水溶性碳氮化物的溶胶-凝胶处理可实现高性能的光阳极

尽管聚合氮化碳（PCN）材料在光电化学（PEC）应用中具有巨大前景，但迄今为止，制造高度稳定且具有光活性的PCN光电极一直是一个遥不可及的目标。在这里，我们通过首次设计一种溶胶-凝胶方法来应对这一挑战，该方法能够轻松地基于属于PCN家族的聚（庚二酰亚胺）（PHI）制备光阳极。溶胶-凝胶工艺利用了由纳米（〜10 nm）颗粒组成的水溶性PHI前驱体的使用，从而可以形成非共价水凝胶。与通常获得的松散附着的厚颗粒涂层相反，水凝胶可以沉积在导电基底上，从而形成机械稳定的多孔聚合物薄层（〜400 nm）。所得的光阳极在中性pH电解液中的甲醇重整中表现出前所未有的PEC性能，在1.23 V vs. RHE时具有177±27 mA（1个阳光照射）cm-2和320±40mA cm-2（2个阳光照射）的非常高的光电流。 ，相对于RHE，光电流低至〜0V。这些参数即使在没有任何外部电偏压的情况下也可以有效运行，如甲醇和甘油的零偏光重整以及4-甲氧基苄醇（4-MBA）的高选择性（〜100％）光氧化所证明的。因此，源自水溶性PCN溶胶-凝胶加工的坚固无粘结剂薄膜代表了基于PCN的高性能“软物质”光电催化系统的新范例。