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susanf金蟲 (小有名氣)
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華東師大課題組在電催化析氫反應(yīng)微觀機(jī)制和反應(yīng)動力學(xué)方面的重要研究進(jìn)展 已有1人參與
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華東師范大學(xué)張坤研究員課題組在電催化析氫反應(yīng)取得重要研究進(jìn)展，論文發(fā)表在jacs au雜志上： 論文鏈接：https://pubs.acs.org/doi/10.1021/jacsau.2c00187 題目：activation of h2o tailored by interfacial electronic states at a nanoscale interface for enhanced electrocatalytic hydrogen evolution 摘要 despite the fundamental and practical significance of the hydrogen evolution reaction (her), the reaction kinetics at the molecular level are not well-understood, especially in basic media. here, with zif-67-derived co-based carbon frameworks (co/ncs) as model catalysts, we systematically investigated the effects of different reaction parameters on the her kinetics and discovered that the her activity was directly dependent not on the type of nitrogen in the carbon framework but on the relative content of surface hydroxyl and water (oh╟/h2o) adsorbed on co active sites embedded in carbon frameworks. when the ratio of the oh╟/h2o was close to 1:1, the co/nc nanocatalyst showed the best reaction performance under the condition of high-ph electrolytes, e.g., an overpotential of only 232 mv at a current density of 10 ma cm╟2 in the 1 m koh electrolyte. we unambiguously identified that the structural water molecules (sws) in the form of hydrous hydroxyl complexes absorbed on metal centers {ohad·h2o@m+} were catalytic active sites for the enhanced her, where m+ could be transition or alkaline metal cations. different from the traditional hydrogen bonding of water, the hydroxyl (hydroxide) groups and water molecules in the sws were mainly bonded together via the spatial interaction between the p orbitals of o atoms, exhibiting features of a delocalized π-bond with a metastable state. these newly formed surface bonds or transitory states could be new weak interactions that synergistically promote both interfacial electron transfer and the activation of water (dissociation of o╟h bonds) at the electrode surface, i.e., the formation of activated h adducts (h*). the capture of new surface states not only explains ph-, cation-, and transition-metal-dependent hydrogen evolution kinetics but also provides completely new insights into the understanding of other electrocatalytic reductions involving other small molecules, including co2, co, and n2. 研究內(nèi)容：迄今為止，還沒有統(tǒng)一的模型來解釋電催化析氫的微觀動力學(xué)，例如ph、堿金屬離子和過渡金屬依賴的反應(yīng)動力學(xué)。使用zif-67衍生的納米結(jié)構(gòu)碳作為原型電催化劑，作者首先提供了確鑿的證據(jù)并證實界面sws以含水羥基絡(luò)合物的形式吸附在金屬{ohad·h2o@m+}（m+是過渡金屬或堿金屬陽離子）是水活化（或離解）和隨后質(zhì)子還原的活性位點。sws中兩個o原子的空間相互作用可能是一種新型的弱相互作用，其強(qiáng)度介于氫鍵和化學(xué)共價鍵之間。此外，由于sws中兩個o原子的p軌道的空間重疊，形成了一個表面瞬態(tài)系綜（方案1c╟e），該系綜協(xié)同促進(jìn)了水和界面電子的激活以及納米尺度界面上的質(zhì)子轉(zhuǎn)移。應(yīng)該強(qiáng)調(diào)的是，這些動態(tài)表面中間態(tài)（pbi）并不穩(wěn)定，這解釋了her（甚至oer和氧還原反應(yīng)）對微環(huán)境的極端敏感性，例如ph和陽離子依賴性效應(yīng)。sw主導(dǎo)的表面瞬態(tài)概念可調(diào)節(jié)her的微觀動力學(xué)，從而優(yōu)化整個電化學(xué)界面，從而提高活性，而不是僅優(yōu)化催化劑結(jié)構(gòu)，這對于設(shè)計更活躍的電化學(xué)界面以進(jìn)行涉及小分子（co2、co、n2、o2和h2）的儲能和轉(zhuǎn)化反應(yīng)至關(guān)重要。 作者強(qiáng)調(diào)了作為析氫催化活性中心的結(jié)構(gòu)水（sws）的概念與氫鍵水的概念完全不同，因為sws是兩個相鄰的水分子，主要通過兩個o原子的p軌道的空間重疊來結(jié)合，形成具有π鍵特征的局部化學(xué)鍵，由于空間軌道重疊，這為通過表面離域進(jìn)行電子轉(zhuǎn)移提供了一個替代通道。sws作為協(xié)同電子和質(zhì)子轉(zhuǎn)移的替代通道，同時作為活化水o╟h鍵的活性位點，這一概念不僅可以為水環(huán)境中納米材料催化反應(yīng)的催化劑或電解質(zhì)的設(shè)計和選擇提供重要指導(dǎo)，包括co2或co還原、氮還原和其他電催化還原反應(yīng)。 全文pdf免費(fèi)鏈接如下：https://pubs.acs.org/doi/pdf/10.1021/jacsau.2c00187 |
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