Abstract

The hydrothermal method has been used to prepare Ni(OH)₂ photocathode. The photoelectrochemical (PEC) reduction of CO₂ over Ni(OH)₂ has been conducted in 0.2 M LiClO₄ in aqueous and N,N-dimethylformamide (DMF) medium under visible light irradiation. The thin film was characterized by XRD, UV–Vis, FTIR, FESEM-EDX, BET analysis, and electrochemical method for the determination of phases, bandgap energy, chemical bonding, surface morphology, elemental compositions, surface area, and electrochemical properties, respectively. Based on UV–Vis spectroscopy, the bandgap energy of Ni(OH)₂ was 1.8 eV which enabled efficient visible light absorption for the photoreaction. The photocurrent density in aqueous and DMF solution at 0.2 V (vs. Ag/AgCl) was 24 mA cm⁻² and 5 mA cm⁻², respectively. Acetaldehyde and methanol are the products in aqueous solution, while formic acid and methanol are the products in DMF, after 6 h of photoelectrolysis. The product formations from the photoelectrochemical reduction of dissolved CO₂ were 612 and 854 ppm in aqueous and DMF, respectively, where the Faradaic efficiency in aqueous and DMF is 24 and 33%, respectively. Furthermore, throughout the PEC study, the transformation of Ni(OH)₂ to NiO plays a significant role in the formation of organic oxygenates from the reduction reaction of CO₂.

Graphic abstract

中文翻译：

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在Ni（OH）2上将溶解的二氧化碳光电化学还原为有机氧化物

摘要

水热法已用于制备Ni（OH）₂光电阴极。在可见光照射下，在含水和N，N-二甲基甲酰胺（DMF）介质中的0.2 M LiClO ₄中，用Ni（OH）₂进行CO ₂的光电化学（PEC）还原。通过XRD，UV-Vis，FTIR，FESEM-EDX，BET分析和电化学方法对薄膜进行表征，分别测定相，带隙能，化学键，表面形态，元素组成，表面积和电化学性质。基于紫外可见光谱，Ni（OH）₂的带隙能为1.8eV，这使得能够有效吸收光反应的可见光。水溶液和DMF溶液在0.2 V（vs。Ag / AgCl）下的光电流密度分别为24 mA cm ^-2和5 mA cm ^-2。经过6小时的光电解，乙醛和甲醇是水溶液中的产物，而甲酸和甲醇是DMF中的产物。在水溶液和DMF中，光化学还原溶解的CO ₂所产生的产物分别为612和854 ppm，其中在水溶液和DMF中的法拉第效率分别为24％和33％。此外，在整个PEC研究中，Ni（OH）₂向NiO的转化在CO还原反应形成有机氧化物中起着重要作用。₂。

图形摘要