Distortion-Induced Interfacial Charge Transfer at Single Cobalt Atom Secured on Ordered Intermetallic Surface Enhances Pure Oxygen Production

Abstract

In this work, atomic cobalt (Co) incorporation into the Pd2Ge intermetallic lattice facilitates operando generation of a thin layer of CoO over Co-substituted Pd2Ge, with Co in the CoO surface layer functioning as single metal sites. Hence the catalyst has been titled Co1–CoO-Pd2Ge. High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy confirm the existence of CoO, with some of the Co bonded to Ge by substitution of Pd sites in the Pd2Ge lattice. The role of the CoO layer in the oxygen evolution reaction (OER) has been verified by its selective removal using argon sputtering and conducting the OER on the etched catalyst. In situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy demonstrate that CoO gets transformed to CoOOH (Co3+) in operando condition with faster charge transfer through Pd atoms in the core Pd2Ge lattice. In situ Raman spectroscopy depicts the emergence of a CoOOH phase on applying potential and shows that the phase is stable with increasing potential and time without getting converted to CoO2. Density functional theory calculations indicate that the Pd2Ge lattice induces distortion in the CoO phase and generates unpaired spins in a nonmagnetic CoOOH system resulting in an increase in the OER activity and durability. The existence of spin density even after electrocatalysis is verified from electron paramagnetic resonance spectroscopy. We have thus successfully synthesized intermetallic supported CoO during synthesis and rigorously verified the role played by an intermetallic Pd2Ge core in enhancing charge transfer, generating spin density, improving electrochemical durability, and imparting mechanical stability to a thin CoOOH overlayer. Differential electrochemical mass spectrometry has been explored to visualize the instantaneous generation of oxygen gas during the onset of the reaction.

Unraveling the Cooperative Mechanisms in Ultralow Copper-Loaded WC@NGC for Enhanced CO2 Electroreduction to Acetic Acid

“…In situ ATR-FTIR spectroscopy (setup Figure S13a) was carried out to detect the crucial intermediates formed during eCO 2 RR and to propose the reaction mechanism. , Figure a displays the time-dependent in situ IR spectra that were taken while eCO 2 RR was performed at different applied potentials. The negative band at 2343 cm –1 observed at all the applied potentials can be attributed to the CO 2 consumption.…”

Nitrogen Doping-Induced Structural Distortion in LaMnO3 Enhances Oxygen Reduction and Oxygen Evolution Reactions

“…Electrochemical oxygen redox reactions, oxygen reduction and water oxidation (ORR and OER), demand efficient catalyst materials to promote energy storage and conversion via metal–air batteries and fuel cells. − As per the Sabatier principle, the volcano plot shows Pt-containing materials and RuO 2 /IrO 2 are best for ORR and OER, respectively, − but their economic nonviability and geographic scarcity severely constrain their widespread applicability. Among different novel material designs, transition-metal oxides have been explored significantly for ORR − (O 2 + H 2 O + 4e – → 4OH – ) and the reverse reaction OER. Manganese oxides have attracted attention, due to its high-abundance, low-cost, and environmetal safety. − Due to the occurrence of different polymorphs of Mn-based oxides with variable Mn-valence, it is challenging to decipher and tune the active sites and give a broad-spectrum overview of its actvity-determining factors. − An explicit understanding of the structure–property relationship with kinetic and mechanistic study is highly essential to generate an understanding of the efficiency of Mn-oxides in oxygen redox reactions.…”