Hydrogen, a versatile energy carrier, is a promising alternative to replace the environmentally harmful and unsustainable use of fossil fuels. This much-touted fuel of the future may however have pitfalls, such as issues associated with hydrogen production, storage, and distribution. Hydrogen storage and distribution are concerned with various technical, environmental and safety issues. Indirect hydrogen storage methods such as – in solid-state materials, ammonia, and methanol/ethanol – are recently being considered by academic and industry parties. Ammonia (NH) can be a promising carbon-free carrier with a high energy density, established transportation network, high hydrogen contents and high flexibility. Hydrogen production from NH decomposition requires catalyst/support such as metal oxides. In binary metal oxides like perovskites and spinels, their unique morphologies and structural flexibility enable to apply defined control over the reaction profile through detailed engineering material design. The focus of this study is to conduct a comprehensive review on the existing and emerging mixed metal oxides catalysts used in the NH decomposition process in hydrogen production. The activity of various mixed metal oxide catalysts is critically assessed, and their resulting performances are discussed in detail. Furthermore, this study covers challenges associated with hydrogen production through the catalytic NH cracking process.

中文翻译：

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绿色制氢催化氨裂解工艺中的混合金属氧化物：综述

氢是一种多功能能源载体，是替代对环境有害且不可持续的化石燃料使用的有前途的替代品。然而，这种备受吹捧的未来燃料可能存在缺陷，例如与氢气生产、储存和分配相关的问题。氢气的储存和分配涉及各种技术、环境和安全问题。学术界和工业界最近正在考虑固态材料、氨和甲醇/乙醇等间接储氢方法。氨（NH）具有高能量密度、完善的运输网络、高氢含量和高灵活性，是一种有前途的无碳载体。 NH 分解产生氢气需要催化剂/载体，例如金属氧化物。在钙钛矿和尖晶石等二元金属氧化物中，其独特的形态和结构灵活性使得能够通过详细的工程材料设计对反应曲线进行明确的控制。本研究的重点是对制氢中 NH 分解过程中使用的现有和新兴混合金属氧化物催化剂进行全面综述。严格评估了各种混合金属氧化物催化剂的活性，并详细讨论了它们的性能。此外，这项研究还涵盖了通过催化 NH 裂解工艺生产氢气的相关挑战。