We report the rational design and fabrication of earth-abundant, visible-light-absorbing Cu₂ZnSnS₄ (CZTS) nanoparticle (NP) in situ sensitized S doped TiO₂ nanoarchitectures for high-efficiency solar water splitting. Our systematic studies reveal that these nanoarchitectures significantly enhance the visible-light photoactivity in comparison to that of TiO₂, S doped TiO₂, and CZTS NP sensitized TiO₂. Detailed photoelectrochemical (PEC) studies demonstrate an unprecedented enhancement in the photocurrent density and incident photon to electron conversion efficiency (IPCE). This enhancement is attributed to the significantly improved visible-light absorption and more efficient charge separation and transfer/transport, resulting from the synergistic influence of CZTS NP sensitization and S doping, which were confirmed by electrochemical impedance spectroscopy (EIS). Moreover, density functional theory (DFT) calculations supported by the experimental evidence revealed that the gradient S dopant concentration along the depth direction of TiO₂ nanorods led to the band gap grading from ∼2.3 to 2.7 eV. This S gradient doping introduced a terraced band structure via upshift of the valence band (VB), which provides channels for easy hole transport from the VB of S-doped TiO₂ to the VB of CZTS and thereby enhances the charge transport properties of the CZTS/S-TNR photoanode. This work demonstrates the rational design and fabrication of nanoarchitectures via band edge engineering to improve the PEC performance using simultaneous earth-abundant CZTS NP sensitization and S doping. This work also provides useful insight into the further development of different nanoarchitectures using similar combinations for energy-harvesting-related applications.

中文翻译：

---

通过带边工程提高了TiO _2的太阳能氧化性能：硫掺杂和富含地球的CZTS纳米颗粒的故事

我们报告了合理设计和制造的土质，可见光吸收铜₂ ZnSnS ₄（CZTS）纳米粒子（NP）原位敏化的S掺杂的TiO ₂纳米结构的高效太阳能水分解。我们的系统研究表明，与TiO ₂，S掺杂的TiO ₂和CZTS NP敏化的TiO ₂相比，这些纳米结构显着增强了可见光光活性。。详细的光电化学（PEC）研究表明，光电流密度和入射光子至电子转换效率（IPCE）的空前提高。这种增强归因于CZTS NP敏化和S掺杂的协同影响，从而显着改善了可见光吸收和更有效的电荷分离和转移/传输，这已通过电化学阻抗谱（EIS）确认。此外，实验证据支持的密度泛函理论（DFT）计算表明，沿TiO ₂深度方向的梯度S掺杂剂浓度纳米棒导致能带隙从约2.3到2.7 eV。这种S梯度掺杂通过价带（VB）的上移引入了阶梯带结构，从而为从S掺杂的TiO ₂的VB到CZTS的VB的空穴传输提供了方便的通道，从而增强了CZTS的电荷传输性能/ S-TNR光电阳极。这项工作通过带边工程证明了合理的设计和制造纳米体系结构，以同时使用富含地球的CZTS NP敏化和S掺杂来提高PEC性能。这项工作还为使用相似的能量收集相关应用组合提供了对不同纳米体系结构进一步开发的有用见解。