Supplementary information files for "S-scheme p-n junction Na0.6CoO2/g-C3N4 heterostructure as an efficient photocatalyst for green hydrogen production: fabrication, characterization and mechanisms"

Supplementary information files for article "S-scheme p-n junction Na0.6CoO2/g-C3N4 heterostructure as an efficient photocatalyst for green hydrogen production: fabrication, characterization and mechanisms"Probing the spatial separation and transport process of photogenerated charges at nanoscale interfaces is essential for understanding catalytic reaction mechanisms on heterostructure photocatalysts. Here, we developed a p-n junction Na0.6CoO2/g-C3N4 S-scheme photocatalyst via electrostatic self-assembly technology. A significant hydrogen production rate of ∼ 0.294 mmol g−1 h−1 was achieved on the optimal Na0.6CoO2/g-C3N4, which was ten times higher than that of pure g-C3N4. In-situ XPS shows that the electrons in Na0.6CoO2/g-C3N4 had different flow directions without and with illumination, demonstrating a built-in electric field being formed through Na0.6CoO2 and g-C3N4 interaction. DFT calculations and ultraviolet photoelectron spectroscopy verified that g-C3N4 and Na0.6CoO2 possess the energy band structures conforming to the heterostructure of S-scheme. In-situ Kelvin probe microscope studies show that Na0.6CoO2 and g-C3N4 both have a self-induced electric field effect, and their combination significantly strengthens the built-in electric field and improves the space separation of photogenerated electrons. Compared with the change of the surface photovoltage of g-C3N4 (60 mV) and Na0.6CoO2 (−30 mV), the average surface contact potential difference of Na0.6CoO2/g-C3N4 reached 320 mV, yielding a higher efficiency of photogenerated electron separation. This work also provides direct evidence on the existence of a built-in electric field and an electron flow direction for heterostructure photocatalyst materials.© The Authors, CC BY 4.0《S型p-n结Na₀.₆CoO₂/g-C₃N₄异质结构用于高效绿色产氢：制备、表征与机制》论文的补充信息文件。探究纳米尺度界面处光生载流子的空间分离与输运过程，是理解异质结构光催化剂催化反应机制的关键所在。本研究通过静电自组装技术，构建了p-n结型Na₀.₆CoO₂/g-C₃N₄ S型光催化剂。最优配比的Na₀.₆CoO₂/g-C₃N₄样品展现出约0.294 mmol·g⁻¹·h⁻¹的优异产氢速率，是纯g-C₃N₄的10倍。原位X射线光电子能谱（In-situ XPS）测试表明，Na₀.₆CoO₂/g-C₃N₄在有、无光照条件下的电子流向存在差异，证实Na₀.₆CoO₂与g-C₃N₄相互作用形成了内建电场。密度泛函理论（DFT）计算与紫外光电子能谱（UPS）验证表明，g-C₃N₄与Na₀.₆CoO₂的能带结构符合S型异质结的能带匹配要求。原位开尔文探针显微镜（In-situ KPM）研究显示，Na₀.₆CoO₂与g-C₃N₄均存在自诱导电场效应，二者复合后显著强化了内建电场，提升了光生电子的空间分离效率。与纯g-C₃N₄（60 mV）和Na₀.₆CoO₂（-30 mV）的表面光电压变化相比，Na₀.₆CoO₂/g-C₃N₄的平均表面接触电势差可达320 mV，实现了更高的光生电子分离效率。本研究还为异质结构光催化剂材料的内建电场存在性与电子流向提供了直接实验证据。© 作者，CC BY 4.0