Determining the Electrochemical Oxygen Evolution Reaction Kinetics of Fe 3 S 4 @Ni 3 S 2 Using Distribution Function of Relaxation Times

First-row transition metal carbonates catalyze the electrochemical oxygen evolution reaction: iron is master of them all

In pursuing green hydrogen fuel, electrochemical water-splitting emerges as the optimal method. A critical challenge in advancing this process is identifying a cost-effective electrocatalyst for oxygen evolution on the anode. Recent research has demonstrated the efficacy of first-row transition metal carbonates as catalysts for various oxidation reactions. In this study, Earth-abundant first-row transition metal carbonates were electrodeposited onto nickel foam (NF) electrodes and evaluated for their performance in the oxygen evolution reaction. The investigation compares the activity of these carbonates on NF electrodes against bare NF electrodes. Notably, Fe2(CO3)3/NF exhibited superior oxygen evolution activity, characterized by low overpotential values, i.e. Iron is master of them all (R. Kipling, Cold Iron, Rewards and Fairies, Macmillan and Co. Ltd., 1910). Comprehensive catalytic stability and durability tests also indicate that these transition metal carbonates maintain stable activity, positioning them as durable and efficient electrocatalysts for the oxygen evolution reaction.

Monometallic interphasic synergy via nano-hetero-interfacing for hydrogen evolution in alkaline electrolytes

Electrocatalytic synergy is a functional yet underrated concept in electrocatalysis. Often, it materializes as intermetallic interaction between different metals. We demonstrate interphasic synergy in monometallic structures is as much effective. An interphasic synergy between Ni(OH)₂ and Ni-N/Ni-C phases is reported for alkaline hydrogen evolution reaction that lowers the energy barriers for hydrogen adsorption-desorption and facilitates that of hydroxyl intermediates. This makes ready-to-serve Ni active sites and allocates a large amount of Ni d-states at Fermi level to promote charge redistribution from Ni(OH)₂ to Ni-N/Ni-C and the co-adsorption of H_ads and OH_ads intermediates on Ni-N/Ni-C moieties. As a result, a Ni(OH)₂@Ni-N/Ni-C hetero-hierarchical nanostructure is developed, lowering the overpotentials to deliver -10 and -100 mA cm^-2 in alkaline media by 102 and 113 mV, respectively, compared to monophasic Ni(OH)₂ catalyst. This study unveils the interphasic synergy as an effective strategy to design monometallic electrocatalysts for water splitting and other energy applications.

Promising Electrocatalytic Water and Methanol Oxidation Reaction Activity by Nickel Doped Hematite/Surface Oxidized Carbon Nanotubes Composite Structures

Tailoring the precise construction of non-precious metals and carbon-based heterogeneous catalysts for electrochemical oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) is crucial for energy conversion applications. Herein, this work reports the composite of Ni doped Fe₂ O₃ (Ni-Fe₂ O₃ ) with mildly oxidized multi-walled CNT (O-CNT) as an outstanding Mott-Schottky catalyst for OER and MOR. O-CNT acts as a co-catalyst which effectively regulates the charge transfer in Ni-Fe₂ O₃ and thus enhances the electrocatalytic performance. Ni-Fe₂ O₃ /O-CNT exhibits a low onset potential of 260 mV and overpotential 310 mV @ 10 mA cm^-2 for oxygen evolution. Being a Mott-Schottky catalyst, it achieves the higher flat band potential of -1.15 V with the carrier density of 0.173×10²⁴  cm^-3 . Further, in presence of 1 M CH₃ OH, it delivers the MOR current density of 10 mA cm^-2 at 1.46 V vs. RHE. The excellent electrocatalytic OER and MOR activity of Ni-Fe₂ O₃ /O-CNT could be attributed to the synergistic interaction between Ni-doped Fe₂ O₃ and O-CNT.