A n-Si/CoOx/Ni:CoOOH photoanode producing 600 mV photovoltage for efficient photoelectrochemical water splitting  

一种能产生600 mV光电压以高效驱动光电化学分解水的n-Si/CoO_(x)/Ni:CoOOH光阳极

作　　者：Zhuocheng Yin Yuchuan Shi Shaohua Shen 阴卓成;石玉川;沈少华(International Research Center for Renewable Energy,State Key Laboratory of Multiphase Flow in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]International Research Center for Renewable Energy,State Key Laboratory of Multiphase Flow in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China

出　　处：《Science China Materials》2022年第12期3442-3451,共10页中国科学（材料科学（英文版）

基　　金：supported by the National Key Research and Development Program of China (2018YFB1502003);the National Natural Science Foundation of China (21875183);the Natural Science Basic Research Program of Shaanxi Province (2019JCW-10);the National Program for the Support of Top-notch Young Professionals;the Fundamental Research Funds for the Central Universities;The Youth Innovation Team of Shaanxi Universities

摘　　要：n-Si,believed as a promising photoanode candidate,has suffered from sluggish oxygen evolution reaction(OER)kinetics and poor chemical stability when exposed to aqueous electrolyte.Herein,CoO_(x)/Ni:CoOOH bilayers were successfully deposited on n-Si substrate by atomic layer-deposition(ALD)and photoassisted electrochemical deposition(PED)for stabilizing and catalyzing photoelectrochemical(PEC)water oxidation.In comparison to the n-Si/CoO_(x)photoanode as reference,the prepared n-Si/CoO_(x)/Ni:CoOOH photoanode upon the optimized PED process presents a much improved PEC performance for water splitting,with the onset potential cathodically shifted to~1.03 V vs.reversible hydrogen electrode(RHE)and the photocurrent density much increased to 20 mA cm^(−2)at 1.23 V vs.RHE.It is revealed that the introduction of Ni dopants increases the work functions of the deposited Ni:CoOOH overlayers,which gives rise to the upward band bending weakened at the n-Si/CoO_(x)/Ni:CoOOH cascading interface while strengthened at the Ni:CoOOH/electrolyte interface(with the band bending shifted from downward to upward),contributing to the decreased and the increased driving forces for charge transfer at the interfaces,respectively.Then,the balanced driving forces at the interfaces would endow the n-Si/CoO_(x)/Ni:CoOOH photoanode with the best PEC performance.Moreover,PED has been evidenced superior to ED to dope Ni into CoOOH with the formed overlayer effectively catalyzing and stabilizing PEC water splitting.n-Si是一种有开发潜力的光阳极材料,但其缓慢的水氧化反应动力学及其在水溶液中易氧化等缺点严重限制了其光电化学分解水性能的提高.基于此,我们通过原子层沉积(ALD)与光辅助电沉积(PED)成功将CoO_(x)/Ni:CoOOH双层结构沉积至n-Si光阳极表面,以此来稳定n-Si光阳极并且加快产氧反应动力学过程.相比于n-Si光阳极,n-Si/CoO_(x)/Ni:CoOOH展现出更好的光电催化分解水性能,其起始电位为1.03 V相比于可逆氢电势(vs.RHE),且光电流密度在1.23 V vs.RHE时可达到20 mA cm^(−2).研究表明,Ni掺杂会减小Ni:CoOOH的功函数,从而使得n-Si/CoO_(x)/Ni:CoOOH串联界面的向上能带弯曲减弱,而Ni:CoOOH/电解液界面的向上能带弯曲增强(其中包括一个能带弯曲由向下变为向上的过程),导致这两处界面上的空穴迁移驱动力分别降低与升高;由此,通过两处界面的载流子驱动力的优化,获得了最佳的光电催化分解水性能.另外,相对于电化学沉积(ED),PED方法在功能薄膜沉积方面表现出更大的优势,PED得到的Ni:CoOOH薄膜的稳定性和活性要优于ED得到的Ni:CoOOH薄膜.

关 键 词：n-Si PHOTOANODE work function photoelectrochemical water splitting 

分 类 号：TQ116.2[化学工程—无机化工]