Hybrids of Cobalt/Iron Phosphides Derived from Bimetal–Organic Frameworks as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

Abstract

The electrochemical splitting of water, as an efficient and large-scale method to produce H, is still hindered by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode. Considering the synergetic effect of the different metal sites with coordination on the surface of electrocatalysts, the hybrids of Co/Fe phosphides (denoted as Co-Fe-P) is prepared by one-step phosphorization of CoFe metal-organic frameworks for the first time as highly efficient electrocatalysts for OER. Benefiting from the synergistic effect of Co and Fe, the high valence of Co ions induced by strongly electronegative P and N and the large electrochemical active surface area (ECSA) originated from exposed nanowires on the surface of Co/Fe phosphides, the resultant Co-Fe-P-1.7 exhibits remarkable electrocatalytic performances for OER in 1.0 M KOH, affording an overpotential as low as 244 mV at a current density of 10 mA/cm, a small Tafel slope of 58 mV/dec, and good stability, which is superior to that of the state-of-the-art OER electrocatalysts. In addition, the two-electrode cell with Co-Fe-P-1.7 modified Ni foam as anode and cathode in an alkaline electrolyte, respectively, exhibits the decomposition potential of ca. 1.60 V at a current density of 10 mA/cm and excellent stability.

Co9S8 Nanoparticles‐Embedded N/S‐Codoped Carbon Nanofibers Derived from Metal–Organic Framework‐Wrapped CdS Nanowires for Efficient Oxygen Evolution Reaction

“…The Nyquist plots exhibited in Figure c reveal that Co 9 S 8 /NSCNFs‐850 has a lower charge transfer resistance at the electrocatalyst–electrolyte interface, suggesting the faster electron transfer process during the electrochemical reaction. The great charge transport ability is mainly endowed by the 1D nanofiber‐like structure, which not only offers abundant active sites for OER process but also accelerates interelectron transport along the entire framework . This result is in accordance with the Tafel slope and both have elucidated the outstanding OER electrocatalytic efficiency of Co 9 S 8 /NSCNFs‐850.…”

“…Electrochemical water splitting is supposed to be one of the most promising and environmentally friendly approaches for the mass production of hydrogen energy . However, the efficiency of water splitting for hydrogen production is limited by the anodic oxygen evolution reaction (OER), which is kinetically sluggish due to the complex four‐electron transportation process, dramatically with a large overpotential as high as 1.23 V (versus reversible hydrogen electrode (RHE)) . Therefore, an effective electrocatalyst is essential for OER to lower the overpotential and promote the reaction process .…”

High Efficiency FeNi‐Metal‐Organic Framework Grown In‐situ on Nickel Foam for Electrocatalytic Oxygen Evolution

“…The C 1s spectra shows three different functional groups (Figure. 3d), namely, the binding energy position of the C=C bond at 284.7 eV, which corresponded to the benzene ring; the C−O at a binding energy of 285.6 eV; and O–C=O (288.5 eV) ,…”

Preparation of Yolk–Shell‐Structured CoxFe1−xP with Enhanced OER Performance

“…In the Fe 2p spectra, peaks at 723.9 and 710.8 eV correspond to Fe 2p 1/2 and Fe 2p 3/2 ,a nd the Fe 2 + and Fe 3 + peaks appear at 712.8 and 710.2 eV,r espectively.A ccording to previous reports, the surfaceF eo ft he Co 0.47 Fe 0.53 P catalystt ends to bind with phosphate. [20] In other words, the high-valence state of Co ions enhances the OH À sorption capacity of the electrocatalyst, [31] which is greatlyb eneficialt oi mproving the OER performance. [32] In addition, positives hifts of binding energies signifyr educed electron occupation leadingt oa robust electron-acceptings ite.…”