Design of semitransparent tantalum nitride photoanode for efficient and durable solar water splitting
Design of semitransparent tantalum nitride photoanode for efficient and durable solar water splitting
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DOI：
10.1039/d2ee02090d
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发表时间：
2022-10-07
影响因子：
32.5
通讯作者：
Domen, Kazunari
中科院分区：
文献类型：
--
作者：
Higashi, Tomohiro;Nishiyama, Hiroshi;Domen, Kazunari
通过光电化学-光伏（PEC-PV）串联装置进行无偏太阳能水分解是一种高效、低成本和可持续制氢以满足不断增长的能源需求的有前景的策略。 Ta3N5的带隙为2.1 eV，太阳能-氢(STH)能量转换效率的理论极限为15.3%，但当Ta3N5用作单个光阳极时，光生空穴的低效利用将STH效率限制在7%。此外，Ta3N5表面的自光氧化导致裸露的Ta3N5表面形成TaOx绝缘层，导致水氧化反应的稳定性较差。在这项研究中，我们制备了一种无空隙 Ta3N5 平面薄膜，该薄膜源自高功率溅射金属 Ta 沉积，然后在高温氨处理中氮化，在透明 GaN/Al2O3 衬底上生长。通过超薄 NiFeOx 电催化剂层对 Ta3N5 表面进行均匀修饰，半透明 Ta3N5 光阳极极大地提高了稳定性，在模拟 AM1.5G 太阳光照下，与可逆氢电极相比，在 1.23 V 下产生了 7.4 mA cm(-2) 的光电流。透明 Ta3N5 光阳极与 CuInSe2 PV 耦合的无辅助水分解被证明具有 9% 的初始 STH 效率，这是金属氧化物/氮化物基 PEC-PV 串联电池中迄今为止报道的最高效率。借助均相电催化剂，串联电池在装置运行长达 2 小时的情况下实现了 4% 的稳定 STH 效率。通过测量和理论建模，确定载流子动力学和传输以确定最关键的 Ta3N5 薄膜参数，以进一步增强性能。
Unbiased solar water splitting via a photoelectrochemical-photovoltaic (PEC-PV) tandem device is a promising strategy for efficient, low-cost, and sustainable hydrogen production to address growing energy demands. The bandgap of Ta3N5 is 2.1 eV for a theoretical limit of solar-to-hydrogen (STH) energy conversion efficiency of 15.3%, but the inefficient utilization of photogenerated holes limits the STH efficiency to 7% when Ta3N5 is used as a single photoanode. In addition, the formation of a TaOx insulating layer on the bare Ta3N5 surface caused by the self-photooxidation of the Ta3N5 surfaces leads to the poor stability of the water oxidation reaction. In this study, we fabricated a void-free Ta3N5 planar thin film, originating from metallic Ta deposition by high-power sputtering followed by nitridation in ammonia treatment at high temperature, grown on a transparent GaN/Al2O3 substrate. With the uniform decoration of the Ta3N5 surface with an ultrathin NiFeOx electrocatalyst layer, the semitransparent Ta3N5 photoanode drastically improved the stability and generated a photocurrent of 7.4 mA cm(-2) at 1.23 V vs. a reversible hydrogen electrode under simulated AM1.5G solar illumination. Unassisted water splitting by a transparent Ta3N5 photoanode coupled with CuInSe2 PV was demonstrated with an initial STH efficiency of 9%, which is the highest efficiency ever reported among metal oxide/nitride-based PEC-PV tandem cells. With the homogeneous electrocatalyst, the tandem cell achieved the stabilized STH efficiency of 4% up to 2 h of device operation. Using measurements and theoretical modeling, the charge carrier kinetics and transport were determined to identify the most crucial Ta3N5-thin-film parameters for further performance enhancement.