Benazzi Elisabetta, Cristino Vito, Boaretto Rita, Caramori Stefano, Natali Mirco
Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via L. Borsari 46, 44121, Ferrara, Italy.
Dalton Trans. 2021 Jan 19;50(2):696-704. doi: 10.1039/d0dt03567j.
The design of active photocathodes for the hydrogen evolution reaction (HER) is a crucial step in the development of dye-sensitized photoelectrochemical cells (DS-PECs) aimed at solar-assisted water splitting. In the present work, we report on the use of orange CdTexS1-x quantum dots (QDs) with an average diameter of ca. 3.5 nm, featuring different capping agents (MAA, MPA, and MSA) for the sensitization of electrodes based on nanostructured NiO. Photoelectrochemical characterization of the resulting NiO|QDs electrodes in the presence of [CoIII(NH3)5Cl]Cl2 as an irreversible electron acceptor elects MAA-capped QDs as the most active sample to achieve substantial photocurrent densities thanks to both improved surface coverage and injection ability. Functionalization of the NiO|QDs electrodes with either heterogeneous Pt or the molecular nickel bis(diphosphine) complex (1) as the hydrogen evolving catalysts (HECs) yields active photocathodes capable of promoting hydrogen evolution upon photoirradiation (maximum photocurrent densities of -16(±2) and -20(±1) μA·cm-2 for Pt and 1 HECs, respectively, at 0 V vs. NHE, 70-80% faradaic efficiency, maximum IPCE of ca. 0.2%). The photoelectrochemical activity is limited by the small surface concentration of the QD sensitizers on the NiO surface and the competitive light absorption by the NiO material which suggests that the match between dye adsorption and the available surface area is critical to achieving efficient hydrogen evolution by thiol-capped QDs.
用于析氢反应（HER）的活性光电阴极的设计是旨在实现太阳能辅助水分解的染料敏化光电化学电池（DS-PEC）发展中的关键一步。在本工作中，我们报道了使用平均直径约为3.5 nm的橙色CdTexS1-x量子点（QD），其具有不同的封端剂（MAA、MPA和MSA）来敏化基于纳米结构NiO的电极。在[CoIII(NH3)5Cl]Cl2作为不可逆电子受体存在的情况下，对所得NiO|QD电极进行光电化学表征，结果表明，由于表面覆盖率和注入能力的提高，MAA封端的QD是最具活性的样品，可实现可观的光电流密度。用非均相Pt或分子镍双（二膦）配合物（1）作为析氢催化剂（HEC）对NiO|QD电极进行功能化，可得到在光照射下能够促进析氢的活性光电阴极（在相对于标准氢电极0 V时，Pt和1 HEC的最大光电流密度分别为-16(±2)和-20(±1) μA·cm-2，法拉第效率为70-80%，最大光电转换效率约为0.2%）。光电化学活性受到NiO表面QD敏化剂的小表面浓度以及NiO材料竞争性光吸收的限制，这表明染料吸附与可用表面积之间的匹配对于通过硫醇封端的QD实现高效析氢至关重要。
