Electrochemical Reduction of Carbon Dioxide and Iron Oxide in Molten Salts to Fe/Fe₃C Modified Carbon for Electrocatalytic Oxygen Evolution

Abstract

Non-noble electrocatalyst for the oxygen evolution reaction (OER) is essential for water electrolysis and electrochemical conversion of CO 2. Integrating electrochemical fixation of CO 2 and electrochemical metallurgy to prepare advanced OER electrocatalyst is a promising solution to promote carbon neutrality and renewable energy. Herein, the electrochemical reduction of CO 2 and Fe 2 O 3 are combined in molten salts to prepare cathodic Fe 3 C-based electrocatalyst and anodic oxygen at 600 8C with enhanced current efficiency. The resulting Fe 3 C-based electrocatalyst outperforms precious electrocatalyst towards the OER operation in 1 M KOH due to a dynamic structural evolution to form an interface of Fe 3 C-FeOOH. The splitting of water and the conversion of CO 2 by electrochemical routes have been regarded as promising strategies to relieve concerns on energy and environmental sustainability. [1-3] The both processes are restricted by the oxygen evolution reaction (OER), which is sluggish in reaction kinetics owing to the four-electron-transfer characteristics. [3] Noble-metal-based catalysts such as ruthenium oxide and iridium oxide possess high activity for OER, but the high cost and scarcity of noble metals limit the large-scale application. Developing high-activity non-noble catalysts for OER is hence of importance. An OER catalyst is expected to possess optimal surface chemistry to ensure active centers with high intrinsic activity, and rationally designed architecture to endow the full exposure of active sites. [1] Iron-based oxides, hydroxides, phosphides, and carbides have widely been explored as nonprecious OER catalysts. [4, 5] In particular, iron carbides with [*] X.

Benchmarking the pH–Stability Relationship of Metal Oxide Anodes in Anion Exchange Membrane Water Electrolysis

“…The SEM images of NiFe 2 O 4 before and after electrolysis in Figure S14 show that the morphology was not changed by the reconstitution of the alkaline electrolyte, but the reconstituted species was unstable in pure water, which increased the surface roughness of the nanoparticles. The Raman spectra of NiFe 2 O 4 in Figure S15 demonstrated that more Ni/FeOOH was generated on the catalyst surface after pre-activation which is stable in pH = 14; however, the intensity of the FeOOH peak located at ∼680 cm –1 decreased after the test in pure water, implying the dissolution of Fe species Figure S16 gives the dissolved metal content in the electrolyte after the 20 h stability test of NiFe 2 O 4 and Ni 0.5 Co 1.5 FeO 4 with or without the pre-activation.…”

Salt-thermal methods for recycling and regenerating spent lithium-ion batteries: a review

“…Benefitting from the high concentration of O 2− in molten carbonates, we can (electro-)chemically synthesize oxide functional materials in molten salts. 119,120 The molten salt can serve as both a promising electrolyte and solvent to electrochemically break the chemical bonds of LTMO, and thereby separate Li-and transition metal species.…”

“…Usually, LiFePO 4 prefers to be oxidized to FePO 4 with the retention of olivine structure and Li is selectively recycled. The oxidation agents are [Fe(CN) 6 ], 3–122 Na 2 S 2 O 8 , 123,124 Fe 2 (SO 4 ) 3 , 125 H 2 O 2 , 126 and air. 127 The oxidation roasting of LiFePO 4 in the air generates Fe 2 O 3 and Li 3 Fe 2 (PO 4 ) 2 , 128 by which the Li and Fe cannot be separated completely.…”