From waste to fuel cells. In situ preparation of an atomically precise Pd(II)-catalyst by selective extraction of Pd(II) from a mixture of metal ions using modified multi walled carbon nanotubes (MWCNTs) and its implementation in the oxygen reduction

Fuel cells can effectively mitigate environmental challenges by enabling clean energy production. A significant obstacle to the implementation of fuel cells is the need for catalysts that make the electrode reactions efficient, especially the oxygen reduction reaction (ORR), allowing to replace the currently used bulk platinum electrodes which are efficient but very expensive. In this paper, we demonstrate that an atomically precise and very efficient Pd(II)-based catalyst for ORR can be easily prepared under environmentally friendly conditions using non-covalently modified multi-walled carbon nanotubes (MWCNT-L) to selectively recover precious Pd(II) from wastewater. Electrodes loaded with the new MWCNT-LPd catalyst, which contains only 1.94 % of Pd(II), give rise to ORR with 90 % H 2 O production (4 e − process), onset potential of 0.846 V (vs RHE) and half-wave potential (E 1/2 ) of 0.657 V, very close to the performance of bulk platinum electrodes. Sustainable energy production and waste management are combined here within the framework of a circular economy criterion that places emphasis on environment protection. • An efficient Pd catalyst for ORR was prepared following a circular economy criterion. • The catalyst was prepared via selective extraction of Pd(II) from wastewater. • The catalysts is assembled via Pd uptake on modified multi-walled carbon nanotubes. • The heterogeneous catalyst is very efficient despite the low Pd(II) loading (1.94 %). • Four-electron reduction of O 2 was achieved with almost exclusive production of H 2 O.