Coordination tuning of Nanoporous Metal Film by Secondary Electrodeposition to Optimize Methanol Electrooxidation Activity

Abstract

This study demonstrates how the crystal structure of nanoporous noble metal films can be precisely controlled by constructing secondary nanostructures via pulsed electrodeposition. The use of secondary deposition techniques preserved the nanoporous morphology while enabling crystal structure adjustment to improve electrochemical performance. Precise control over the crystal structure of the nanoporous metal film was employed to selectively suppress the growth of the gold (Au) (220) crystallographic plane in NPGFs because of its lower catalytic activity compared to the Au (111) plane. The observed phenomenon can be attributed to the recovery of interfacial ionic concentration near the electrode surface during the non-electrolyzing pulse-off phase. Crystallographic analysis of the optimized pulsed-NPGF film revealed a reduced intensity for the Au (220) plane and a corresponding increase in intensity for the Au (110) plane. This modification enhances the ECSA and improves the catalytic performance of the MOR. The reduction in charge transfer resistance due to the controlled crystal structure is electrochemically reflected as a cathodic shift in the onset potential and an increase in peak current density compared with NPGFs and DC NPGFs. In addition, a significant improvement in the stability of the pulsed-deposited films was observed. The pulsed-NPGF shows a higher peak current density than NPGF over 100 MOR cycles under alkaline conditions, and it maintains superior current density with less decay during prolonged chronoamperometry testing in the MOR. This study offers important insights into the design of nanoporous metal films, illustrating how the crystal structure can be manipulated to enhance the catalytic performance for electrochemical applications.