Mechanism of oxygen vacancy assisted water-splitting of LaMnO3: inorganic perovskite prediction for fast solar thermochemical H2 production,Inorganic Chemistry Frontiers

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Mechanism of oxygen vacancy assisted water-splitting of LaMnO3: inorganic perovskite prediction for fast solar thermochemical H2 production
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2020-05-06 , DOI: 10.1039/d0qi00338g
Mingkai Fu _{1,

2,

3,

4} , Huajun Xu _{5,

6,

7,

8} , Xin Li _{1,

2,

3,

4,

9}

Affiliation

Highly reducible and thermally stable lanthanum–manganese perovskites represent a promising class of materials for solar thermochemical hydrogen production. However, such materials suffer from a low hydrogen production rate, resulting in an incomplete re-oxidation yield. To enhance the kinetic performance, the mechanism of water-splitting and hydrogen production around the oxygen vacancy of the LaMnO₃(010) defective surface is revealed. A transition state with the activation energy E_a = 126.45 kJ mol⁻¹ is explored in the rate-determining step of hydrogen transfer from superficial O to neighbor Mn. Based on the analysis of the E_a results, the H₂ production time ratio between La_0.9Sr_0.4MnO₃ and La_0.9Sr_0.1MnO₃ is 47.3, close to the experimental data from the literature. Also, the kinetic unfavourability of Sr and the favorability of Al and Ga are predicted, which are in good agreement with previous experimental phenomena. Moreover, La_0.875Sr_0.125Mn_0.875Mo_0.125O₃ is suggested as a promising material to rapidly produce H₂. All the results demonstrate the effectiveness of the proposed water-splitting mechanism and provide an easy access for fast determination of kinetically favorable dopants for lanthanum–strontium–manganese perovskites.

中文翻译：

LaMnO3的氧空位辅助水分解机理：无机钙钛矿预测快速太阳能热化学法制氢

高度可还原且热稳定的镧锰钙钛矿代表了太阳能热化学制氢的有前途的材料类别。然而，这些材料的氢产生速率低，导致不完全的再氧化产率。为了增强动力学性能，揭示了LaMnO ₃（010）缺陷表面的氧空位附近水分解和产氢的机理。在氢从表层O转移到邻域Mn的速率确定步骤中，研究了活化能E _a = 126.45 kJ mol ^-1的过渡态。基于对E _a结果的分析，La之间的H ₂产生时间比_0.9 Sr_0.4 MnO₃和La_0.9 Sr_0.1 MnO₃为47.3，接近文献中的实验数据。而且，预测了Sr的动力学不利性以及Al和Ga的有利性，这与先前的实验现象非常吻合。此外，建议使用La_0.875 Sr_0.125 Mn_0.875 Mo_0.125 O₃作为快速产生H₂的有前途的材料。所有结果证明了所提出的水分解机理的有效性，并为快速测定镧-锶-锰钙钛矿的动力学上有利的掺杂剂提供了方便。

更新日期：2020-05-06

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