Milla Suominen

Li-ion batteries (LIBs) are one of the most deployed energy storage technologies worldwide, providing power for a wide range of applications—from portable electronic devices to electric vehicles (EVs). The growing demand for LIBs, coupled with a shortage of critical battery materials, has prompted the scientific community to seek ways to improve material utilization through the recycling of end-of-life LIBs. While valuable battery metals are already being recycled on an industrial scale, graphite—a material classified as a critical resource—continues to be discarded. In this study, graphite waste recovered from the recycling of LIBs was successfully upcycled into an active graphite/rGO (reduced graphene oxide) composite oxygen electrocatalyst. The precursor graphite for rGO synthesis was also extracted from LIBs. Incorporating rGO into the graphite significantly enhanced the specific surface area and porosity of the resulting composite, facilitating effective doping with residual metals during subsequent nitrogen doping via pyrolysis. These composite catalysts enhanced both the oxygen reduction and oxygen evolution reactions, enabling their use as air electrode catalyst materials in zinc–air batteries (ZABs). The best-performing composite catalyst demonstrated an impressive power density of 100 mW cm⁻² and exceptional cycling stability for 137 h. This research further demonstrates the utilization of waste fractions from LIB recycling to drive advancements in energy conversion technologies.

SnO _x has received great attention as an electrocatalyst for CO ₂ reduction reaction (CO ₂ RR), however; it still suffers from low activity. Moreover, the atomic‐level SnO _x structure and the nature of the active sites are still ambiguous due to the dynamism of surface structure and difficulty in structure characterization under electrochemical conditions. Herein, CO ₂ RR performance is enhanced by supporting SnO ₂ nanoparticles on two common supports, vulcan carbon and TiO ₂ . Then, electrolysis of CO ₂ at various temperatures in a neutral electrolyte reveals that the application window for this catalyst is between 12 and 30 °C. Furthermore, this study introduces a machine learning interatomic potential method for the atomistic simulation to investigate SnO ₂ reduction and establish a correlation between SnO _x structures and their CO ₂ RR performance. In addition, selectivity is analyzed computationally with density functional theory simulations to identify the key differences between the binding energies of ^* H and ^* CO ₂ ⁻ , where both are correlated with the presence of oxygen on the nanoparticle surface. This study offers in‐depth insights into the rational design and application of SnO _x ‐based electrocatalysts for CO ₂ RR.

Out of the transition metals capable of electrochemical carbon dioxide reduction, Pd is interesting as it can convert carbon dioxide electrochemically into formate or carbon monoxide depending on the applied potential. In fact, it is capable of producing formate at the most positive known potentials that are close to zero overpotentials although at an unfortunately low activity and at the cost of deactivation by carbon monoxide poisoning. One aim is to improve the activity and stability of Pd-based electrocatalysts towards formate production in low overpotentials. As Pd is a critical raw material, we also wish to decrease the amount of Pd required while maintaining high carbon dioxide electroreduction capability. These goals can be achieved by nanostructuring and supporting the Pd catalyst. Here, we have employed a simple wet impregnation synthesis approach to prepare small nanoparticles and nanowires of Pd supported on single walled carbon nanotubes and tested the optimum loading of Pd to obtain high formate yield with improved activity and stability. Reactive sites can be created on the carbon support by subjecting it to ozonation prior to supporting the metal, which may help certain interesting nanostructures, such as nanowires, to grow. Additionally, the oxygen functional groups on the carbon surface are expected to affect the wettability of the electrode which is important for achieving an efficient carbon dioxide electroreduction and a longer-term stability of the reaction. Therefore, we also studied the effects of ozonation of the carbon supports on the electrochemical reduction of carbon dioxide into both formate and syngas (mixture of hydrogen and carbon monoxide) on Pd. Carbon atoms inevitably participate in hydrogen evolution reaction and, thus, in syngas production on Pd-supported catalysts at higher overpotentials. Our results show that ozonation greatly enhances the activity of the catalyst material and improves its stability when applying low overpotentials for formate formation in comparison to the pristine carbon support. The current density on Pd supported ozone treated carbon nanotube material remains stable over 4h of carbon dioxide electrolysis at an applied potential of -0.45 V (vs. RHE) while Pd on pristine carbon support deactivates during the initial 30 min of the experiment. Longer electrolysis times do reveal slow changes in product distribution although activity on ozone-treated single walled carbon nanotube-supported catalyst is excellent. Additionally, the different support materials cause interesting changes in product selectivity upon applying higher overpotentials for the production of syngas. Pd supported on pristine nanotubes produces syngas with carbon monoxide-to-hydrogen ratios of 0.72 and 1.38 at applied potentials of -0.85 V (vs. RHE) and -0.95 V (vs. RHE), respectively, while ozone treated material produces less than 10% of carbon monoxide. Through physico-chemical characterizations of the materials we aim at understanding the observed changes in electrochemical reduction of carbon dioxide on carbon supported Pd nanostructures.