A robust iron oxyhydroxide water oxidation catalyst operating under near neutral and alkaline conditions

Abstract

Iron oxyhydroxide thin films electrochemically deposited from a non-aqueous medium using metal inorganic complexes as a metal ion precursor have been demonstrated as an efficient electrochemical water oxidation catalyst under near neutral as well as alkaline pH conditions.

Interconnected Network of Core–Shell CoP@CoBiPi for Efficient Water Oxidation Electrocatalysis under Near Neutral Conditions

“…[45][46][47] We quantified the active sites from the oxidation peak in the LSV cure of CoP@CoBiPI/Tia nd the integrated charge should be proportional to the total number of active sites. This value compares favorably to the behavioro fm any other reported OER catalysts in near neutralm edium, such as NiBi/ITO (36 h À1 , h = 610 mV,I TO:i ndium-doped tin oxide), [39] FeBi/ITO (612 h À1 , h = 600 mV), [41] NiO x /FTO (39.6-54 h À1 , h = 610 mV,F TO:f luorine-doped tin oxide), [44] and CoW/FTO (36 h À1 , h = 640 mV). This value compares favorably to the behavioro fm any other reported OER catalysts in near neutralm edium, such as NiBi/ITO (36 h À1 , h = 610 mV,I TO:i ndium-doped tin oxide), [39] FeBi/ITO (612 h À1 , h = 600 mV), [41] NiO x /FTO (39.6-54 h À1 , h = 610 mV,F TO:f luorine-doped tin oxide), [44] and CoW/FTO (36 h À1 , h = 640 mV).…”

“…The spot pattern for the crystalline core phase can be clearly seen, but weak diffuse rings from the amorphousC oBiPi shell are also observed. Bare Ti mesh shows no OER activity.T he activated precursor (cobalt hydroxide) requires an overpotential of 770 mV to reach 10 mA cm À2 .C oP NA/Tii s active for OER electrocatalysisr equiringa no verpotential of 530 mV to approach1 0mAcm À2 .I nc ontrast, CoP@CoBiPi/Ti shows RuO 2 /Ti-like OER activity and only requires al ower overpotentialo f4 10 mV to reach 10 mA cm À2 .T his overpotential compares favorably to the behavior of reported non-noble metal-borate OER catalysts in KBi electrolytes, including CoBi (h 1mAcm À2 = 390 mV), [28] NiBi (h 1mAcm À2 = 540 mV), [39] NiBi film (h 1mAcm À2 = 384 mV), [40] FeBi (h 1mAcm À2 = 490 mV), [41] and CuBi (h 10 mA cm À2 = 801 mV). The binding energies (BEs) at 191.6 eV for B1s ( Figure 2a [36,37] Figure2ds hows the XPS spectrumo fC o2p, and the 2p 3/2 and 2p 1/2 peaks at 780.5 and 795.5 eV are in ar ange typical of Co 2 + or Co 3 + bound to oxygen.…”

Cobalt Phosphonates as Precatalysts for Water Oxidation: Role of Pore Size in Catalysis

“…To rationalize the steady increase in catalytic activity from CoOP‐0 to CoOP‐15, areal capacitances ( C DL , mF cm 2 ), electrochemically accessible surface areas (ECSA), and roughness factors (RF) were determined by using CV in a non‐faradaic zone (potential region: −0.05–0.05 V vs. Ag/AgCl; see the Supporting Information for calculation methodology) …”

Core–Shell‐Structured NiS2@Ni‐Bi Nanoarray for Efficient Water Oxidation at Near‐Neutral pH

“…in which J is the current density, A is the geometrical electrode area, and 4 expresses the moles of electron consumed in generating one mole of O 2 . The TOF for NiS 2 @Ni‐B i /CC was calculated to be 0.28 mol O 2 s −1 at an overpotential of 500 mV, and additional TOF values for NiS 2 @Ni‐B i /CC are shown in Figure c. Notably, NiS 2 @Ni‐B i /CC has a higher TOF than reported non‐noble metal water oxidation electrocatalysts at a fixed overpotential ( η ), including NiO x ‐en/FTO (0.015 mol O 2 s −1 , η= 610 mV; en=1,2‐diaminoethane, FTO=fluorine‐doped tin oxide), Ni‐B i (0.01 mol O 2 s −1 , η =600 mV), FeOOH/ITO (0.17 mol O 2 s −1 , η =600 mV), Fe‐based film/GC (0.21 mol O 2 s −1 , η =530 mV; GC=glassy carbon) …”