Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy.

Wenchao Sheng,Jie Zheng,Yushan Yan,Jingguang G Chen,Minrui Gao,Zhongbin Zhuang

doi:10.1038/ncomms6848

Wenchao Sheng, Jie Zheng + Show 4 more

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https://doi.org/10.1038/ncomms6848

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Abstract

The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. The identification of the reaction descriptor is therefore of critical importance for the rational catalyst design and development. Here we report the correlation between hydrogen oxidation/evolution activity and experimentally measured hydrogen binding energy for polycrystalline platinum examined in several buffer solutions in a wide range of electrolyte pH from 0 to 13. The hydrogen oxidation/evolution activity obtained using the rotating disk electrode method is found to decrease with the pH, while the hydrogen binding energy, obtained from cyclic voltammograms, linearly increases with the pH. Correlating the hydrogen oxidation/evolution activity to the hydrogen binding energy renders a monotonic decreasing hydrogen oxidation/evolution activity with the hydrogen binding energy, strongly supporting the hypothesis that hydrogen binding energy is the sole reaction descriptor for the hydrogen oxidation/evolution activity on monometallic platinum.

Highlights

The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems
Recent studies combining density functional theory (DFT) calculations and experimental data demonstrate that the HER kinetics in terms of exchange current density in both low- and high-pH regimes correlate to DFT-calculated hydrogen binding energies (HBEs) via a volcano relationship, indicating that HBE can be used as the reaction descriptor for the HER2,11
A bifunctional mechanism has been proposed, which involves the participation of adsorbed OH in the oxidation of H2, while Durst et al find that the HBE values acquired from cyclic voltammograms (CVs) in strong acid are smaller than those in strong base, and ascribe the slower HOR/HER kinetics in base to the stronger HBE

Summary

Introduction

The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. A bifunctional mechanism has been proposed, which involves the participation of adsorbed OH in the oxidation of H2 (refs 20,23), while Durst et al find that the HBE values acquired from cyclic voltammograms (CVs) in strong acid are smaller than those in strong base, and ascribe the slower HOR/HER kinetics in base to the stronger HBE. This hypothesis is supported by the larger discharging resistance for underpotentially deposited hydrogen (HUPD) in base than in acid from impedance measurements[22], suggesting that the HBE value should be the main reaction descriptor. The monotonically decreased HOR/HER activities correlate well with the continuously strengthened electrochemical HBE values, strongly supporting the hypothesis that HBE is the sole reaction descriptor of the HOR/HER kinetics

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