Identifying a Universal Activity Descriptor and a Unifying Mechanism Concept on Perovskite Oxides for Green Hydrogen Production

Producing indispensable hydrogen and oxygen for social development via water electrolysis shows more prospects than other technologies. Although electrocatalysts have been explored for centuries, a universal activity descriptor for both hydrogen-evolution reaction (HER) and oxygen-evolution reaction (OER) is not yet developed. Moreover, a unifying concept is not yet established to simultaneously understand HER/OER mechanisms. Here, the relationships between HER/OER activities in three common electrolytes and over ten representative material properties on 12 3d-metal-based model oxides are rationally bridged through statistical methodologies. The orbital charge-transfer energy (Δ) can serve as an ideal universal descriptor, where a neither too large nor too small Δ (≈1 eV) with optimal electron-cloud density around Fermi level affords the best activities, fulfilling Sabatier's principle. Systematic experiments and computations unravel that pristine oxide with Δ ≈ 1 eV possesses metal-like high-valence configurations and active lattice-oxygen sites to help adsorb key protons in HER and induce lattice-oxygen participation in the OER, respectively. After reactions, partially generated metals in the HER and high-valence hydroxides in the OER dominate proton adsorption and couple with pristine lattice-oxygen activation, respectively. These can be successfully rationalized by the unifying orbital charge-transfer theory. This work provides the foundation of rational material design and mechanism understanding for many potential applications

Elements of computer-aided design and manufacturing/ Pao

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High-efficiency electrosynthesis of hydrogen peroxide from oxygen reduction enabled by a tungsten single atom catalyst with unique terdentate N(1)O(2) coordination

First published: 31 December 2021Single-atom catalysts (SACs) have shown great potential in the electrochemical oxygen reduction reaction (ORR) toward hydrogen peroxide (H2O2) production. However, current studies are mainly focused on 3d transition-metal SACs, and very little attention has been paid to 5d SACs. Here, a new kind of W SAC anchored on a porous O, N-doped carbon nanosheet (W1/NO-C) is designed and prepared via a simple coordination polymer-pyrolysis method. A unique local structure of W SAC, terdentate W1N1O2 with the coordination of two O atoms and one N atom, is identified by the combination of aberration-corrected scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption fine structure spectroscopy. Remarkably, the as-prepared W1/NO-C catalyzes the ORR via a 2e– pathway with high onset potential, high H2O2 selectivity in the wide potential range, and excellent operation durability in 0.1 m KOH solution, superior to most of state-of-the-art H2O2 electrocatalysts ever reported. Theoretical calculations reveal that the C atoms adjacent to O in the W1N1O2-C moiety are the most active sites for the 2e– ORR to H2O2 with the optimal binding energy of the HOO* intermediate. This work opens up a new opportunity for the development of high-performance W-based catalysts for electrochemical H2O2 production.Feifei Zhang, Yinlong Zhu, Cheng Tang, Yu Chen, Binbin Qian, Zhiwei Hu, Yu-Chung Chang, Chih-Wen Pao, Qian Lin, Seyedeh Alieh Kazemi, Yun Wang, Lian Zhang, Xiwang Zhang, and Huanting Wan