Fe‐CoP Electrocatalyst Derived from a Bimetallic Prussian Blue Analogue for Large‐Current‐Density Oxygen Evolution and Overall Water Splitting

Abstract

Industrial application of overall water splitting requires developing readily available, highly efficient, and stable oxygen evolution electrocatalysts that can efficiently drive large current density. This study reports a facile and practical method to fabricate a non‐noble metal catalyst by directly growing a Co‐Fe Prussian blue analogue on a 3D porous conductive substrate, which is further phosphorized into a bifunctional Fe‐doped CoP (Fe‐CoP) electrocatalyst. The Fe‐CoP/NF (nickel foam) catalyst shows efficient electrocatalytic activity for oxygen evolution reaction, requiring low overpotentials of 190, 295, and 428 mV to achieve 10, 500, and 1000 mA cm−2 current densities in 1.0 m KOH solution. In addition, the Fe‐CoP/NF can also function as a highly active electrocatalyst for hydrogen evolution reaction with a low overpotential of 78 mV at 10 mA cm−2 current density in alkaline solution. Thus, the Fe‐CoP/NF electrode with meso/macropores can act as both an anode and a cathode to fabricate an electrolyzer for overall water splitting, only requiring a cell voltage of 1.49 V to afford a 10 mA cm−2 current density with remarkable stability. This performance appears to be among the best reported values and is much better than that of the IrO2‐Pt/C‐based electrolyzer.

Fluoridated Iron–Nickel Layered Double Hydroxide for Enhanced Performance in the Oxygen Evolution Reaction

“…Therefore, the phase structure transfer from the metalÀO bondingi nt he FeNi-LDHs to metalÀFb onding after fluoridation is significant to the OER process because of the facile formation of metal (oxy)hydroxide over the surface. [17] Similar to that work, we propose the real active structure to be core-shell structured FeNioxy/hydroxide over the iron-nickel fluorides urface, and the active sites can be assigned to the Fe-doped high-valenceN i-(oxy)hydroxide in situ formed over the iron-nickel fluorides urface. These catalysts act as the "pre-catalyst" rather than the real reactive species, and the presence of nonmetallic elements in the catalystw as speculated to generatem ore vacancies or defects around the metal cations by dissolution (as demonstrated by Chen and co-workersf or the Co-based catalyst through as eries of operando measurements), which will facilitate the structuralt ransformation into the real reactive species of high-valence metal oxyhydroxide for OER.…”

“…Moreover,t he preferential active sites were Ni rather than Fe in the FeNi catalyst system because the binding energies of Fe to the OER intermediates (*OH, *O, and *OOH) were too strong to be desorbed, whereas the presenceo fF ec an promote the Ni/Co-based catalystf or OER because of the synergistic effect of different cations in the catalyst system. [17] Similar to that work, we propose the real active structure to be core-shell structured FeNioxy/hydroxide over the iron-nickel fluorides urface, and the active sites can be assigned to the Fe-doped high-valenceN i-(oxy)hydroxide in situ formed over the iron-nickel fluorides urface.…”

“Nano-garden cultivation” for electrocatalysis: controlled synthesis of Nature-inspired hierarchical nanostructures

“…The patterns show four distinct peaks at 31.7, 36.2, 46.3, and 48.2 , which can be assigned to the (011), (111), (112) and (211) planes of the orthorhombic CoP phase (JCPDS no: 29-0497), respectively. [47][48][49][50] Particularly, the corresponding SEM X-ray energy dispersive spectra (EDX) and the high-resolution transmission electron microscopy (HRTEM) micrograph in Fig. S8 and S9 † also veried the formation of CoP.…”

Engineering Ternary Pyrite‐Type CoPS Nanosheets with an Ultrathin Porous Structure for Efficient Electrocatalytic Water Splitting

“…[12][13][14]34,35] To get a deeper understanding of the OER process, a series of characterizations of CoPS UPNSs before and after OER were carried out, including XPS spectrum, Raman spectrum, XRD, and TEM. [36,37] Additionally, the proportion of Co 3 + has increased, indicated by the formation of CoOOH. The peaks of Co 2 + remain unchanged while, in contrast, the peaks of Co 3 + have shifted to a higher valance.…”

“…The peaks at 780.1 and 795.4 eV are attributed to the Co 3 + of CoOOH. [36,37] Additionally, the proportion of Co 3 + has increased, indicated by the formation of CoOOH. The PÀ O bond and SÀ O bond become dominant in the P 2p spectra and S 2p spectra ( Figure S13b and c) respectively, indicating electrochemical oxidation during the OER process.…”