Abstract
Discovering low-cost, durable and highly active electrocatalysts with reduced use of precious platinum group metals (PGM) as catalysts for the hydrogen evolution reaction (HER), the oxygen reduction reaction (ORR), and the oxygen evolution reaction (OER) is a key step for large-scale adaptation of fuel cells, electrolyzers, and metal-air batteries. Here we explore the stability and reaction mechanisms of synthesized one-dimensional transition metal dithiolene wire (TM-DWs, TM = Cr – Cu, Rh, Ir, Pt, Pd) for the ORR and the OER in acid solution by density functional theory (DFT) calculations. Our calculations reveal that Co-DW intrinsically exhibits high catalytic activity for bi-functional ORR/OER with low limiting overpotentials (η) of 0.46/0.45 V via four-electron reactions. These low limiting overpotentials arise from modified scaling relations by strengthening the binding free energy of OOH* compared to OH* on TM-DWs, yielding universal minimum ORR/OER overpotentials of η = 0.28/0.22 V, remarkably decreased compared to both metal and oxide surfaces (ηideal = 0.37 V). By applying uni-axial strain, the adsorption strength of reaction intermediates on TM reactive sites can be optimized due to shifts in d-band centers. Our findings provide valuable insight into rational design of non-precious metals based electrocatalysts, and demonstrate a new strategy of tuning adsorptions via uni-axial strain to develop efficient bifunctional electrocatalysts of ORR/OER under optimal conditions.
Highlights
With rising concerns about limited fossil fuel resources, air pollution and climate changes, there are intense worldwide efforts to utilize more sustainable and renewable energy sources
This significant improvement arises from modified scaling relations by strengthening binding free energy of OOH compared to OH on TM-DWs, yielding universal bifunctional minimum oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) overpotentials of
The oxygen reduction reaction and oxygen evolution reaction catalyzed by TM-DWs
Summary
With rising concerns about limited fossil fuel resources, air pollution and climate changes, there are intense worldwide efforts to utilize more sustainable and renewable energy sources. Key technologies in the sustainable chain are electrochemical storage and conversion devices, such as metal-air batteries, water splitting systems, and proton exchange membrane (PEM) fuel cells (FC)[1,2]. The most important challenges are related to the much slower kinetics of the cathode than the anode reaction (hydrogen oxidation reaction) and the utilization of precious metals, which greatly hinder large-scale industrial applications[3]. The hydrogen and oxygen evolution reaction (HER/OER) relevant to water splitting electrocatalysts requires catalysts based on noble metals[4,5,6]. Great effort in recent years has been devoted by researchers working in this area, there are a large number of such earth-abundant materials that are electrocatalytically active for either ORR or OER.
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