Sustained and Efficient Ethanol Oxidation by Tethering Tunable N-Donors Onto Integrated MXene/Pd-Electrodes

The practical development of ethanol fuel cells as a future energy technology is currently set back by fundamental roadblocks (low cycling stability) and design shortcomings, e.g., poorly-defined active sites and underexplored electrode integration strategies. Here, a rational design of 3D layered integrated electrodes is introduced for Pd-catalysed ethanol oxidation, in which chemically grafted pyrrolic or picolinic amide linkers are employed to co-anchor Pd nanoparticles on an MXene support via a "hand-in-hand" molecular coordination mode. This approach leads to good directional exposure of Pd (111) crystal surfaces through tailored ligand-metal-support interactions, creating well-defined, more efficient Pd catalytic sites; thereby, the inherent limitations of the random distribution of the palladium surface sites can be overcome. The resulting system incorporating pyrrolic ligands exhibits excellent cycling stability (up to 10 000 cycles with 97.9% capacity retention), making it one of the most efficient ethanol oxidation catalysts reported. The robust Pd immobilisation after MXene functionalisation with the pyrrolic linkers allows achieving this performance with low Pd loadings, while calculations also indicate weaker adsorption of catalyst-poisoning oxidation intermediates. This new, modular approach provides a pathway to more efficient electrocatalytic systems for real-world applications in ethanol fuel cells.