光電化學（photoelectrochemical，PEC）水分解因能夠直接利用太陽能將水裂解為氫氣與氧氣，被認為是一種極具潛力的綠色氫能生產技術。近年來，三斜釩酸鐵（triclinic iron vanadate，FeVO4）因其適當的能隙、高理論光電流密度及優異的穩定性，成為PEC電極材料的研究熱點。此外，釩酸鐵由地球上豐富的元素組成，具備低成本、大規模生產的潛力。然而，塊狀釩酸鐵材料在PEC水分解應用中的效率受到其較差的電荷傳輸能力與有限的光吸收範圍的限制。因此，透過形貌調控將釩酸鐵轉變為奈米結構，以提升比表面積、表面缺陷、增強電荷分離效率，已成為改善其光電催化性能的重要策略。而二硫化鎢（tungsten disulfide，WS2）具備獨特的層狀結構與高導電性，可作為助催化劑促進電荷轉移，進一步降低析氧反應（Oxygen evolution reation，OER）反應的過電位，從而提升水分解反應速率。透過二硫化鎢的修飾，釩酸鐵電極可有效減少載流子復合現象，顯著提高PEC光電流密度，進而增強外加偏壓光-電轉換效率（Applied Bias Photon-to-current Efficiency，ABPE）。目前，我們已成功使用水熱合成法及高溫段燒法合成出不同形貌且高結晶度的釩酸鐵，並透過液相剝離法製備二硫化鎢奈米片。接著進一步將兩者複合形成二硫化鎢修飾釩酸鐵（FeVO4/WS2）異質結構（heterostructure）電極，以提升PEC水分解效能。電化學測試結果顯示，二硫化鎢修飾釩酸鐵電極在模擬太陽光照條件下表現出顯著提升的光電流響應，與釩酸鐵相比，其PEC性能得到顯著改善，光電流密度最高提升至原先的3倍，ABPE則提高至原先的10倍。本研究首次提出以二硫化鎢修飾釩酸鐵異質結構作為PEC光陽極的設計策略，為未來PEC水分解技術提供新的發展方向。透過材料形貌調控、缺陷工程與異質結構的結合，本研究有望為可再生氫能生產提供更具競爭力的解決方案，並推動PEC技術在太陽能轉換與清潔能源領域的實際應用。

This study presents the development and characterization of FeVO4/WS2 heterostructures for enhanced photoelectrochemical (PEC) water splitting applications. Iron vanadate (FeVO4) was synthesized via a hydrothermal method with systematic pH adjustment (pH 1, 2, 4, 7, 10) to achieve morphological control, resulting in various nanostructures ranging from nanorods and nanoparticles to nanopolyhedra. Among these morphologies, FeVO4 nanorods demonstrated superior charge separation efficiency, making them optimal candidates for PEC applications. To further enhance performance, WS2 nanosheets prepared through liquid-phase exfoliation (LPE) were integrated with FeVO4 to construct FeVO4/WS2 heterostructures using a drop-coating technique. Comprehensive characterization through X-ray diffraction (XRD), Scanning Electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscope (XPS) confirmed successful synthesis of FeVO4, WS2 nanosheets and heterostructure formation. XPS analysis revealed significant changes in elemental valence state ratios upon heterojunction formation, with pristine FeVO4 F2 sample showing optimal defect concentration characterized by moderate oxygen vacancy (4.17%) and V4+ (18.97%) ratios. After WS2 modification, increases in oxygen vacancies and V4+ concentrations were observed across all samples. The systematic increase in oxygen vacancy and V4+ confirmed electron transfer from WS2 to FeVO4, establishing FeVO4 as the electron acceptor and WS2 as the electron donor within the heterostructure. Mott-Schottky analysis confirmed the formation of an n-n type heterojunction, with both pristine FeVO4 and WS2 exhibiting n-type semiconducting behavior. The decreased slope observed in FeVO4/WS2 heterostructures indicated increased carrier concentration, contributing to improved electrical conductivity and charge transport properties. Ultraviolet photoelectron spectroscopy (UPS) revealed Type-II band alignment, facilitating spatial separation of photogenerated charge carriers and suppressing recombination processes. Linear sweep voltammetry (LSV) measurement demonstrated F2 sample exhibits the best PEC performance among pristine FeVO4. After modified with WS2 nanosheets, FeVO4/WS2 heterostructures exhibiting 2 to 3-fold increases in photocurrent density and approximately 10-fold improvements in applied bias photon-to-current efficiency (ABPE) compared to pristine FeVO4. These significant enhancements were attributed to the synergistic effects of morphology control, defect engineering, and heterojunction formation, which collectively addressed the intrinsic limitations of conventional FeVO4 photoanodes. This research represents the first report of FeVO4/WS2 heterostructures for PEC applications and provides valuable insights into the design of efficient solar-driven water splitting systems. The successful integration of morphology engineering with heterojunction design offers a promising strategy for developing sustainable hydrogen production technologies, demonstrating the potential of semiconductor heterostructures in advancing renewable energy applications.

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