Wood‐Inspired Binder Enabled Vertical 3D Printing of g‐C 3 N 4 /CNT Arrays for Highly Efficient Photoelectrochemical Hydrogen Evolution

2D nanomaterials are very attractive for photoelectrochemical applications due to their ultra‐thin structure, excellent physicochemical properties of large surface‐area‐to‐volume ratios, and the resulting abundant active sites and high charge transport capacity. However, the application of commonly used 2D nanomaterials with disordered‐stacking is always limited by high photoelectrode tortuosity, few surface‐active sites, and low mass transfer efficiency. Herein, inspired by wood structures, a vertical 3D printing strategy is developed to rapidly build vertically aligned and hierarchically porous graphitic carbon nitride/carbon nanotube (g‐C 3 N 4 /CNT) arrays by using lignin as a binder for efficient photoelectrochemical hydrogen evolution. Arising from the directional electron transport and multiple light scattering in the out‐of‐plane aligned and porous architecture, the resulting g‐C 3 N 4 /CNT arrays display an outstanding hydrogen evolution performance, with the hydrogen yield up to 4.36 µmol (cm −2 h −1 ) at a bias of −0.5 V versus RHE, 12.7 and 41.6 times higher than traditional thick g‐C 3 N 4 /CNT and g‐C 3 N 4 films, respectively. Moreover, this 3D printed structure can overcome the agglomeration problem of the commonly used g‐C 3 N 4 with powder configuration and shows desirable recyclability and stability. This facile and scalable vertical 3D printing strategy will open a new avenue to highly enhance the photoelectrochemical performance of 2D nanomaterials for sustainably production of clean energy.