Ultrafast Combustion Synthesis of Robust and Efficient Electrocatalysts for High-Current-Density Water Oxidation

Abstract

The scalable production of inexpensive, efficient, and robust catalysts for oxygen evolution reaction (OER) that can deliver high current densities at low potentials is critical for the industrial implementation of water splitting technology. Herein, a series of metal oxides coupled with Fe2O3 are in situ grown on iron foam massively via an ultrafast combustion approach for a few seconds. Benefiting from the three-dimensional nanosheet array framework and the heterojunction structure, the self-supporting electrodes with abundant active centers can regulate mass transport and electronic structure for prompting OER activity at high current density. The optimized Ni(OH)2/Fe2O3 with robust structure can deliver a high current density of 1000 mA cm–2 at the overpotential as low as 271 mV in 1.0 M KOH for up to 1500 h. Theoretical calculation demonstrates that the strong electronic modulation plays a crucial part in the hybrid by optimizing the adsorption energy of the intermediate, thereby enhancing the efficiency of oxygen evolution. This work proposes a method to construct cheap and robust catalysts for practical application in energy conversion and storage.

Self-Enhancement of Water Electrolysis by Electrolyte-Poled Ferroelectric Catalyst

“…The utilized and pristine Ag/ AgCl electrodes were first calibrated in pure H 2 -saturated 0.1 M KOH electrolyte to acquire the exact potentials relative to the RHE, estimated as −0.958 V and −0.960 V, respectively (Figure S11a). All RHE potentials presented in this work were converted from the utilized Ag/AgCl electrode potential based on the following equation: E RHE = E (Ag/AgCl) + 0.958 V. 21 We sequentially recorded the opencircuit voltage of the utilized Ag/AgCl electrode before the test, after a 48 h chronoamperometry test, and after an additional 48 h chronopotentiometry test, against a pristine Ag/AgCl electrode. The observed variations of the utilized Ag/AgCl electrode for these longterm stability tests were within the range of 0.004 V, a magnitude significantly smaller than the alterations induced by the changes in BFO (Figure S11b).…”

Tuning the Surface Electronic Structure of Amorphous NiWO4 by Doping Fe as an Electrocatalyst for OER

“…During water electrolysis, oxygen evolution reaction (OER) which occurs at the anode is more sluggish kinetic due to four-electron transfer which leads to increase in the activation energy barrier . Till date, transition metal oxides such as ruthenium and iridium (RuO 2 and IrO 2 ) are regarded as effective noble electrocatalysts for the OER reaction in alkaline condition. , However, their scarcity and high cost are unsuitable for large-scale usage. − Therefore, researchers have to design a low cost, earth abundant transition metal-based catalyst possessing a low overpotential and high stability toward hydrogen generation in large scale as compared to noble metals. − Transition metal hydroxides, oxides, phosphides, ,, and chalcogenide-based materials have been regarded as efficient electrocatalysts toward water splitting at various pH conditions. , However, the obtained hydroxide or oxide during OER will act as the electrochemically active site of numerous catalysts which are mentioned above. − Among the above-mentioned electrocatalysts, nickel-based oxides exhibited high OER activity, especially in alkaline environments. , The mixture of 3d transition metal and 4d transition metal oxides displayed notable electrocatalytic activity. , In this point, tungstate-based materials have been brought into consideration for total water splitting. , Among several catalysts, tungstate and molybdate-based materials have attracted much attention among the researchers, and addition of iron over 4d transition metal oxides ensured enhancement in an electrocatalytic performance . Also, heteroatom doping is a most effective route to create deformation of atoms by lattice strain, which greatly enhances the intrinsic activity of a catalyst .…”

Facilitating Reconstruction of the Heterointerface Electronic Structure by the Enriched Oxygen Vacancy for the Oxygen Evolution Reaction

“…In response to today’s ever-increasing global energy and environmental issues, the quest for sustainable and clean energy systems is constantly on the move. The electrochemical oxygen evolution reaction (OER) has been envisioned as playing an unequivocally vital role in a variety of decarbonized energy storage and energy conversion technologies, including water electrolyzers, rechargeable metal–air batteries, regenerative fuel cells, and electrochemical CO 2 reduction. , However, the sluggish kinetics associated with the four sequential proton-coupled electron-transfer processes involved in the OER (4OH – → 2H 2 O + O 2 + 4e – in base), which rely on two steps of O–H bond cleavage and one rigid OO bond formation, severely compromise the overall efficiency of electrochemical systems. − Up to now, in order to promote the reaction rate, noble metal-based catalysts, such as commercial RuO 2 and IrO 2 oxides, still occupy the benchmark position in the OER catalysts, while their unaffordable price and scarcity severely restrict their commercialization in practical devices. − With such concerns, relentless efforts from both industry and academia alike have been devoted to the development of a myriad of alternative OER catalysts based on cost-effective elements (Ni, Co, Fe, and Mn) or their compounds, which would be a very promising answer to the aforesaid problems. − In particular, earth-abundant and environmentally friendly transition metal oxides (TMOs), especially Ni-based materials, have exhibited excellent performance in OER catalysis, taking advantage of their reasonable activity and reactivity, since the OER activities of single TMOs follow the order NiO x > CoO x > FeO x > MnO x . Although encouraging progress has been made, the deficiency of highly active reactive sites, low intrinsic conductivity, and wide energy bandgap of NiO-based catalysts are still major obstacles to the replacement of OER catalysts based on precious metals. − …”