钠-氧海水电池作为一种新型的储能技术备受关注,但其受天然海水介质影响存在氧电极反应动力学缓慢等局限,限制了其实际应用.本研究基于分子设计和纳米技术构筑了一种富含苯并噻二唑的p型聚合物(BK)包覆的n型氧化钛纳米棒异质结阵列光电极(BK@TiO2),通过挖掘两组分的优势和多尺度协同作用,探究异质结效应和大规模阵列的结构优势,使得BK@TiO2光电极实现了良好的光电流响应和双功能氧催化活性.利用BK@TiO2组装而成的光辅助钠-氧海水电池可耦合外加光场,并利用光生载流子加速海水电池反应动力学,在光照下实现了同步增强的充电和放电性能.在0.05 mA cm-2电流密度下,电池的充电电压从黑暗条件下的4.6 V vs.Na/Na+下降至光照条件下2.2 V vs.Na/Na+,而放电电压从1.4 V vs.Na/Na+提升至1.8 V vs.Na/Na+,实现了电池往返效率的显著提升(从30.4％上升至81.8％).结果表明,外层BK聚合物不仅可作为空穴捕获层,与内层TiO2形成的p-n结可诱导强的内建电场,显著增强光生电荷的空间分离效率,还能够作为双功能氧催化活性层,实现光增强的电化学性能.
Construction and performance of novel organic/inorganic p-n heterojunction array photoelectrodes for light-assisted seawater batteries
Sodium-oxygen seawater batteries have attracted much attention as a novel energy storage technology,but their limitations such as slow reaction kinetics of the oxygen electrode due to the influence of natural seawater medium have restricted their practical applications.In this study,a benzothiadiazole-rich p-type polymer(BK)-coated n-type titanium oxide nanorods heterojunction array photoelectrode(BK@TiO2)was constructed based on molecular design and nanotechnology,and by exploring the respective merits of the two components and their synergy,the heterojunction effect and the structural advantages of large-scale array,the newly-developed BK@TiO2 photoelectrode achieves high photocurrent response and bifunctional oxygen catalytic activity simultaneously.The BK@TiO2 enabled light-assisted seawater Na-air rechargeable batteries(LSRBs)can couple the external light field and accelerate the reaction kinetics of the seawater battery using photogenerated carriers to achieve synchronously enhanced charging and discharging performances under light.At a current density of 0.05 mA cm,the charging voltage of the cell decreased from 4.6 V vs.Na/Na+under dark conditions to 2.2 V vs.Na/Na+under light conditions,whereas the discharging voltage was enhanced from 1.4 V vs.Na/Na+to 1.8 V vs.Na/Na+,which achieved a significant enhancement in the round-trip efficiency of the cell(from 30.4％to 81.8％).The results show that the outer BK polymer can not only act as a hole trapping layer,and paring with the inner TiO2 layer for the p-n junction formation can induce a strong built-in electric field to significantly enhance the spatial separation efficiency of photogenerated charges,but also can act as a responsive bifunctional oxygen-catalyzed active layer to achieve photo-enhanced electrochemical performance.
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