Engineering electrocatalysts from wastes: A novel boriding strategy to valorize waste printed circuit boards

Significance 

With the alarming depletion of fossil fuels, climate change and environmental degradation, environment sustainability and energy security have become a top priority. To this end, widespread adoption of renewable energy is deemed a promising strategy for meeting the growing global energy demands and addressing the related environmental issues. Most of the existing renewable energy conversion techniques are based on oxygen evolution reaction (OER), which is characterized by low efficiency due to sluggish kinetics. Addressing this limitation requires designing low-cost and high-performance catalysts for OER, which remains a big challenge.

Transition metal-based nanomaterials are an emerging lot for excellent OER catalysts. Generally, most transition metal-based electrocatalysts can undergo surface reconstruction during catalytic processes even though the surface evolution of multimetal-based catalysts and the structural-property relationship remains poorly understood. Considering the critical role of anions and cations in driving OER activity and properties, their regulation could lead to excellent transition metal-based electrocatalysts.

Synthesizing functional materials from waste has both environmental and economic benefits. Recycling and reusing urban solid wastes, especially recycling critical metals from electronic and electrical wastes like waste printed circuit boards (WPCBs), have drawn considerable attention, given their high economic value. Nevertheless, efficient recovery of the precious metals is yet to be fully realized, resulting in human health issues, severe ecosystem degradation and economic losses. This calls for an urgent design of a highly efficient recycling process for the effective management of WPCBs.

Herein, Dr. Zhijie Chen and Professor Bing-Jie Ni from the University of Technology Sydney together with Professor Hong Chen from the Southern University of Science and Technology developed a facile boriding strategy for direct conversion of multimetal cations in leachates of WPCBs into magnetic mixed metal borides (FeNiCuSnBs) for OER catalysts. This strategy involved integrating high-efficiency oxygen evolution catalysts with accelerated surface reconstruction from WPCBs. A total of four FeNiCuSnB samples, namely FNCSB-1 to FNCSB-4, were prepared via boriding chemical reaction and investigated. Their work is currently published in the journal, Applied Catalysis B: Environmental.

The authors reported the efficient recovery of Fe, Sn, Cu and Ni at a high metal cation recovery rate of 99.78%, 99.49%, 99.96% and 99.98%, respectively. The resulting as-mixed metal boride catalysts, especially those with higher Fe and Ni ratios, exhibited excellent catalytic performance for OER. Remarkably, the optimized FNCSB-4 sample exhibited good stability in alkaline solution and only needed a low overpotential of 199 mV to achieve a current density of 100 mA cm-2, representing the highest activity among the previously reported catalysts and studied waste-derived OER electrocatalysts.

An ex-situ characterization technique was adopted to elucidate the structure-activity relationship. Further mechanism analysis showed that the multimetal borides underwent an accelerated surface self-reconstruction induced by B/Sn etching and facilitated by the formation of the multimetal (oxy)hydroxides that served as active species for oxygen evolution. In addition, the amorphous feature, efficient charge/mass transfer and hierarchical structure also enhance the OER performance.

In summary, the authors are the first to develop a facile and efficient boriding strategy for the direct conversion of leachates of WPCBs into magnetic mixed metal borides for efficient OER. In addition to offering more insights into the correlation between the OER activity and surface self-reconstruction of the multimetal boride-based catalysts, the study findings also offered an efficient and sustainable strategy for recovering precise metals from electrical and electronic wastes. In a statement to Advances in Engineering, the first author, Dr. Zhijie Chen said that the proposed new strategy is a useful approach for regenerating efficient catalysts for high-efficiency critical metal recovery and reutilization.

Engineering electrocatalysts from wastes: A novel boriding strategy to valorize waste printed circuit boards - Advances in Engineering
Scheme 1. Illustration of engineering electrocatalysts from waste printed circuit boards (WPCBs) via a boriding route.

About the author

Dr. Zhijie Chen received his Ph.D. degree in Environmental Engineering from the University of Technology Sydney (UTS), Australia in 2022. He received his B.S. and M.S. degrees from the Wuhan University of Technology in 2015 and 2018, respectively. He now works as a research staff in the Centre for Technology in Water and Wastewater (CTWW), School of Civil and Environmental Engineering, UTS. His research mainly work focuses on the design and synthesis of cost-effective functional materials for advanced energy and environmental applications (e.g., water electrolysis, wastewater reutilization, water purification). He has published ~50 papers in peer-reviewed renowned journals, such as Applied Catalysis B: Environmental, Nano Energy, Green Chemistry, Water Research, and Chemical Engineering Journal.

About the author

A/Prof. Hong Chen obtained his Ph.D. in Inorganic Chemistry from Stockholm University, Sweden. He is now an Associate Professor at the School of Environmental Science and Engineering, Southern University of Science and Technology, China. His research interests mainly focus on resource recycling and utilization chemistry, energy conversion, and environmental remediation. He has published more than 100 refereed journal papers with a citation of over 6,000 and an H-index of 42. He is an Associate Editor of Environmental Chemistry Letters, an Editorial Board member of Sustainable Horizons, Environmental Function Materials, and a Youth Editorial Board Member of Chinese Chemical Letters and Chemical Engineering Journal Advances.

About the author

Prof. Bing-Jie Ni received his Ph.D. degree in environmental engineering in June 2009. He joined the Technical University of Denmark as a postdoctoral research fellow in September of 2009 and then joined The University of Queensland in February 2011 as a senior research fellow. He currently is a full professor in environmental engineering. He has been working in the field of renewable energy production, particularly the interface between chemical engineering and environmental technology. His work focuses on the integration of these disciplines to develop innovative and sustainable technological solutions to achieve efficient energy generation from renewable resources.

Reference

Chen, Z., Zheng, R., Zou, W., Wei, W., Li, J., Wei, W., Ni, B., & Chen, H. (2021). Integrating high-efficiency oxygen evolution catalysts featuring accelerated surface reconstruction from waste printed circuit boards via a boriding recycling strategy. Applied Catalysis B: Environmental, 298, 120583.

Go To Applied Catalysis B: Environmental

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