Pd Ion‐Exchange and Ammonia Etching of a Prussian Blue Analogue to Produce a High‐Performance Water‐Splitting Catalyst

Abstract

The authors report an ammonia‐assisted in situ cation‐exchange method for the synthesis of dodecagon N‐doped PdCoNi carbon‐based nanosheets (Pd‐e‐NiCo‐PBA‐C) and explore the catalytic performance. Pd‐e‐NiCo‐PBA‐C exerts extremely low overpotential and Tafel slope for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) both in acidic and alkaline media, only 47 mV, 55 mV dec−1 (pH = 0, HER) and 147 mV, 67 mV dec−1 (pH = 14, HER), and 309 mV, 67 mV dec−1 (pH = 14, OER), outperforming commercial IrO2‐based and Pt‐based catalysts. In addition, after 5000 cycles, the linear sweep voltammetry curve shows a negligible shift, indicating excellent stability performance. To test its overall water‐splitting performance, Pd‐e‐NiCo‐PBA‐C is applied as both cathode and anode materials. A high current density of 33 mA cm−2 at a battery voltage of 1.6 V is obtained, with the catalytic activity maintained at 97.3% after over 50 h. To get a further insight into the superior OER and HER performance, theoretical calculations are carried out, the better performance originates from the affinity difference of Pd and Ni atoms for gas atoms, and the replacement of inert atoms can decrease the binding energy and enhance the electrocatalytic activity.

Anodic Transformation of a Core‐Shell Prussian Blue Analogue to a Bifunctional Electrocatalyst for Water Splitting

“…In the OER mechanism, dominated by lattice oxygen, cations on the catalyst are continuously leached as the number of cycles increases, which leads to an increase of catalytic activity. [ 44–47 ]…”

“…In the OER mechanism, dominated by lattice oxygen, cations on the catalyst are continuously leached as the number of cycles increases, which leads to an increase of catalytic activity. [44][45][46][47] To detect the interfacial resistance of the corresponding process, electrochemical impedance spectroscopy was performed (Figure 5i, inset). The inset shows the equivalent electric circuit used.…”

Magnetocatalysis: The Interplay between the Magnetic Field and Electrocatalysis

“…The Tafel slope values suggest a two-electron transfer process following a Volmer-Heyrovsky mechanism. [36] As the figure of merit of overpotential is highly dependent on the specific surface areas and number of active sites, the turnover frequency (TOF) is used to reveal the intrinsic electrocatalytic activity of the Heusler bulk crystals. [37] For this purpose, the electrochemical active surface areas (ECSAs) were determined from doublelayer capacitance measurements (Calculation details in the supporting information, Figure S9-14).…”

Using Metal Cation to Control the Microstructure of Cobalt Oxide in Energy Conversion and Storage Applications

“…The peaks of the Co‐h compound at 1542, 1406, 1034, and 677 cm −1 are assigned to the CO stretching mode, OH bending mode, CO stretching mode, and OH bending mode, respectively, in agreement with the XPS spectra of Co‐h compound (Figure 3c). [ 40–42 ] The sharp peaks at 656 and 563 cm −1 in the spectrum of Cl‐Co 3 O 4 ‐h are associated with Co II ‐Co III ‐O vibration in the tetrahedral hole and O‐Co III 3 vibration in the octahedral hole in the spinel lattice, respectively. [ 43,44 ] The analysis revealed the complete decomposition of the compound into Co 3 O 4 phase.…”