Anodic Transformation of a Core‐Shell Prussian Blue Analogue to a Bifunctional Electrocatalyst for Water Splitting. (1st September 2021)

• Record Type: Journal Article
• Authors: Zhang, Hao; Li, Peng; Chen, Shengli; Xie, Fang; Riley, D. Jason
• Is Part Of: Advanced functional materials. Volume 31:Number 48(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-01
• Subjects: amorphous shell -- deprotonation -- electrocatalysis -- Prussian blue analogues -- transformation; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.202106835
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Developing low‐cost oxygen evolution reaction (OER) catalysts with high efficiency and understanding the underlying reaction mechanism are critical for electrochemical conversion technologies. Here, an anodized Prussian blue analogue (PBA) containing Ni and Co is reported as a promising OER electrocatalyst in alkaline media. Detailed post‐mortem characterizations indicate the transformation from PBA to Ni(OH)2 during the anodic process, with the amorphous shell of the PBA facilitating the transformation by promoting greater structural flexibility. Further study with operando Raman and X‐ray photoelectron spectroscopy reveal the increase of anodic potential improves the degree of deprotonation of the transformed core‐shell PBA, leading to an increase of Ni valence. Density functional theory calculations suggest that the increase of Ni valence results in a continuous increase in the adsorption strength of oxygen‐containing species, exhibiting a volcano relationship against the OER activity. Based on the experiments and calculated results, an OER mechanism for the transformed product is proposed. The fully activated catalyst also works as the cathode and the anode for a water‐splitting electrolysis cell with a high output current density of 13.7 mA cm −2 when a cell voltage of 1.6 V applied. No obvious performance attenuation is observed after 40 h of catalysis. Abstract : The transformation of a Prussian blue analogue (NiCo‐PBA) to a layered metal hydroxide by anodization is investigated. Two PBAs are considered, a simple crystalline NiCo‐PBA and a crystalline NiCo‐PBA with an amorphous shell designed to prevent the disintegration of the material upon transformation. The as‐formed materials are characterized and the electrocatalytic performance and underlying mechanism are analyzed in detail.