Purpose

This study compares prior life cycle assessment (LCA) studies on graphene-based materials (GBMs) with new results from original data on ball milling of few-layer graphene. The analysis thus offers an overview of the current state of knowledge on the environmental sustainability of GBM production. Possible future development pathways and knowledge gaps are identified and explained to provide guidance for the future development of GBMs.

Methods

Comparable scopes, aggregation levels, and impact assessment methods are used to analyse diverse GBMs with three different functional units for graphene oxide, pristine graphene, and other GBMs with different carbon/oxygen ratios or thickness. The ecoinvent v3.4 cut-off database is used for background data in all models to provide a common basis of comparison. Furthermore, uncertainty calculations are carried out to give insights on the current level of knowledge and to check if GBM production methods can be differentiated. Finally, a sensitivity analysis is performed on the energy inputs with a detailed description of three future scenarios for the European electricity mix.

Results and discussion

The general analysis of all results highlights three key strategies to improve the environmental sustainability of GBM production. (1) The use of decarbonised energy sources reduces substantially the impacts of GBMs. This benefit is decreased, however, when conservative forecasts of the future European electricity mix are considered. (2) Increased energy efficiency of production is useful mainly for the processes of electrochemical exfoliation and chemical vapour deposition. (3) The principles of green chemistry provide relevant ideas to reduce the impacts of GBMs mainly for the processes of chemical and thermal reduction and for the production of graphene oxide. Furthermore, the analysis of new data on ball milling production reveals that transforming GBM solutions into dry-mass can substantially increase the environmental impacts because of the energy-intensive nature of this conversion. The uncertainty analysis then shows that it is still difficult to differentiate all production methods with the current knowledge on this emerging technology.

Conclusions

With our current level of knowledge on GBMs, it is clear that more accurate data is needed on different production methods to identify frontrunners. Nevertheless, it seems that unknowns, like the state of future electricity mixes, might not often hinder such comparisons because conservative forecasts bring similar changes on many production options. Additionally, functional properties and toxicity for GBMs will require further attention to improve our confidence in the comparison of production methods in the future.

中文翻译：

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致力于更环保地生产石墨烯基材料

目的

这项研究将先前对基于石墨烯的材料（GBM）的生命周期评估（LCA）研究与基于多层石墨烯球磨的原始数据的新结果进行了比较。因此，该分析提供了有关GBM生产环境可持续性的当前知识状态的概述。确定并解释了可能的未来发展途径和知识差距，为GBM的未来发展提供指导。

方法

可比较的范围，聚集水平和影响评估方法用于分析具有三个不同功能单元的各种GBM，这些功能单元包括氧化石墨烯，原始石墨烯和其他具有不同碳/氧比或厚度的GBM。ecoinvent v3.4截止数据库用于所有模型中的背景数据，以提供比较的通用基础。此外，进行不确定性计算以提供有关当前知识水平的见解，并检查GBM生产方法是否可以区分。最后，对能量输入进行了敏感性分析，并详细描述了欧洲电力结构的三种未来情况。

结果与讨论

对所有结果的总体分析突出了提高GBM生产环境可持续性的三个关键策略。（1）使用脱碳能源可大大减少GBM的影响。但是，如果考虑到对未来欧洲电力结构的保守预测，这种收益就会降低。（2）提高生产的能源效率主要用于电化学剥离和化学气相沉积的过程。（3）绿色化学原理为减少GBM的影响提供了相关的思路，主要用于化学和热还原过程以及氧化石墨烯的生产。此外，对球磨生产的新数据的分析表明，由于这种转换的能源密集型性质，将GBM解决方案转换为干质量可以大大增加对环境的影响。然后，不确定性分析表明，利用这种新兴技术的最新知识，仍然很难区分所有生产方法。

结论

凭借我们目前对GBM的知识水平，很明显，在不同生产方法上需要更准确的数据来识别领先者。但是，似乎未知的情况（例如未来的电力混合状况）可能不会经常阻碍这种比较，因为保守的预测会在许多生产方案上带来类似的变化。此外，GBM的功能特性和毒性将需要进一步关注，以提高我们对未来生产方法比较的信心。