Silver nanostructure-modified graphite electrode for in-operando SERRS investigation of iron porphyrins during high-potential electrocatalysis

Abstract

In-operando spectroscopic observation of the intermediates formed during various electrocatalytic oxidation and reduction reactions is crucial to propose the mechanism of the corresponding reaction. Surface enhanced resonance Raman spectroscopy coupled to rotating disc electrochemistry (SERRS-RDE), developed about a decade ago, proved to be an excellent spectroscopic tool to investigate the mechanism of heterogeneous oxygen reduction reaction (ORR) catalysed by synthetic iron porphyrin complexes under steady state conditions in water. The mechanistic information helped develop better ORR catalysts with 2nd sphere residues in the porphyrin rings. To date, the application of this SERRS-RDE setup is limited to ORR only because the thiol self-assembled monolayer (SAM) modified Ag electrode, used as the working electrode in these experiments, suffers from stability issues at more cathodic and anodic potential where H2O oxidation, CO2 reduction, H+ reduction reaction occurs. The current investigation shows the development of 2nd generation SERRS-RDE setup consisting of Ag-nanostructure (AgNS) modified graphite electrode as the working electrode. These electrodes show higher stability (compare to the conventional thiol SAM modified Ag electrode) upon exposure to very high cathodic and anodic potential with a good signal to noise (S/N) ratio in the Raman spectra. The behaviour of this modified electrode towards ORR is found to be the same as SAM modified Ag electrode and same ORR intermediates are observed during electrochemical ORR. At higher cathodic potential the signatures of Fe(0) porphyrin, an important intermediate in H+ and CO2 reduction reactions, was observed at the electrode-water interface in-operando.

Peripheral nucleic bases boost H2production by synthetic molecular catalysts in acidic water

“…[3][4][5] Nocera and Dey have included specifically positioned protic functionalities around a metalloporphyrin core to enhance their H 2 production reactivity. 6,7 Analogously, Cao and co-workers appended protic groups even via a polymeric scaffold on the fringe of metalloporphyrins containing variable first-row transition metals to induce H 2 production. [8][9][10] Bren, Shafaat and Artero have deployed peptides to explore a new facet of synthetic OCS feature that has positively impacted the HER activity in an aqueous medium.…”