Sunlight-driven water splitting to produce hydrogen and oxygen provides a pathway to store available solar energy in the form of stable, energy-dense chemical bonds. Here we investigate a tandem particle-suspension reactor design for solar water splitting comprising micron-scale photocatalyst particles suspended in an aqueous solution with soluble redox shuttles. A porous separator facilitates redox species transport between the hydrogen and oxygen evolution reaction compartments while averting gas crossover. A two-dimensional, transient model of the reactor is presented to illustrate the coupling between light absorption, interfacial electron-transfer kinetics and species transport, and their combined impacts on overall solar-to-hydrogen conversion efficiency. The volumetric reactivity of the suspended semiconductor particles is dictated by combining the (photo)current–voltage behavior of a photodiode with Butler–Volmer electron-transfer kinetics. For the first time, a quantitative approach to determine the impacts of surface-dependent redox shuttle kinetic parameters on reaction selectivity in a Z-scheme system is established. Model results provide insights on the effects of optical, transport and kinetic properties of the semiconductor particles and the redox shuttles on the overall reactor performance. Solar-to-hydrogen reactor efficiencies predicted with BiVO₄ particles for oxygen evolution are at least two times larger than efficiencies achieved with wider band-gap TiO₂ particles due to enhanced visible light absorption; hydrogen evolution with SrTiO₃:Rh particles was considered for both cases. Superior performance is predicted with proton-coupled electron transfer redox shuttles (para-benzoquinone/hydroquinone and iodide/iodate) that absorb little-to-no visible light, while also facilitating operation at near-neutral pH conditions, as compared to the non-proton-coupled triiodide/iodide and iron(III)/iron(II) redox shuttles. For 1 cm tall reaction compartments, diffusive species transport is fast enough to sustain reactor operation at a 1% solar-to-hydrogen conversion efficiency for both para-benzoquinone/hydroquinone and iodate/iodide redox shuttles with less than 2.2 mg L⁻¹ of each of BiVO₄ and SrTiO₃:Rh particles in the solution.

中文翻译：

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通过运输和动力学建模 评估Z方案太阳能水分解的颗粒悬浮反应堆设计†

阳光驱动的水分解产生氢气和氧气，提供了一种以稳定的，能量密集的化学键形式存储可用太阳能的途径。在这里，我们研究了用于太阳能水分解的串联颗粒悬浮反应器设计，该设计包括用可溶解的氧化还原梭悬浮在水溶液中的微米级光催化剂颗粒。多孔隔板促进了氧化还原物质在氢气和氧气逸出反应隔室之间的运输，同时避免了气体交叉。提出了反应器的二维瞬态模型，以说明光吸收，界面电子转移动力学和物质传输之间的耦合，以及它们对总的太阳能到氢转化效率的综合影响。悬浮的半导体颗粒的体积反应性是通过结合光电二极管的（光）电流-电压行为与Butler-Volmer电子转移动力学来决定的。首次建立了定量方法来确定表面依赖的氧化还原穿梭动力学参数对Z方案系统中反应选择性的影响。模型结果提供了有关半导体颗粒和氧化还原梭的光学，传输和动力学特性对整体反应器性能的影响的见解。BiVO预测的太阳能到氢反应堆效率 建立了一种定量方法来确定表面依赖的氧化还原穿梭动力学参数对Z方案系统中反应选择性的影响。模型结果提供了有关半导体颗粒和氧化还原梭的光学，传输和动力学特性对整体反应器性能的影响的见解。BiVO预测的太阳能到氢反应堆效率 建立了一种定量方法来确定表面依赖的氧化还原穿梭动力学参数对Z方案系统中反应选择性的影响。模型结果提供了有关半导体颗粒和氧化还原梭的光学，传输和动力学特性对整体反应器性能的影响的见解。BiVO预测的太阳能到氢反应堆效率由于增强的可见光吸收，用于放氧的_4种颗粒至少比使用带隙较宽的TiO ₂颗粒获得的效率大两倍。两种情况都考虑了用SrTiO ₃：Rh颗粒析氢。质子耦合的电子转移氧化还原梭（对-苯醌/氢醌和碘化物/碘酸盐）可吸收几乎没有可见光，同时与在非中性pH条件下相比，在非中性pH条件下操作也可实现优异的性能。质子偶联的三碘化物/碘化物和铁（ III）/铁（ II））氧化还原梭。对于1厘米高反应隔室，扩散物种传输是足够快的在两种1％的太阳能到氢气转换效率，以维持反应器操作对位苯醌/氢醌和碘酸盐/碘化物氧化还原往复剂小于2.2毫克的L ^-1的溶液中分别含有BiVO ₄和SrTiO ₃：Rh颗粒。