Activating Hematite Nanoplates via Partial Reduction for Electrocatalytic Oxygen Reduction Reaction

Abstract

For redox-active hematite (α-Fe2O3) materials, the adverse electroconductivity deeply obstructs the electrocatalytic activity. Herein, a series of iron oxides including α-Fe2O3 nanoplates, α-Fe2O3/Fe3O4 composites, and Fe3O4 material was prepared via a controllable reduction treatment on α-Fe2O3 precursor. When these iron oxides were characterized as electrocatalysts for oxygen reduction reaction (ORR), it was found that α-Fe2O3 nanoplates could be effectively activated via the reduction treatment. In particular, as the combined merits of composition optimization and electroconductivity improvement, the as-reduced composite consisting of α-Fe2O3 (49.6%) and Fe3O4 (50.4%) achieved the best activity of reaching the current density of 4.90 mA cm–2 at the potential of 0.4 V versus reversible hydrogen electrode (RHE) accompanied by a Tafel slope of 76 mV dec–1 and a high selectivity for four-electron pathway, surpassing single-phase α-Fe2O3 and Fe3O4, as well as other congeneric iron oxide composites. This high performance may offer a great potential of developing electrocatalysts with optimized composition and physicochemical properties.

Hematite as an Electrocatalytic Marker for the Study of Archaeological Ceramic Clay bodies: A VIMP and SECM Study**

“…According to Compton et al, [4] in neutral media, hematite acts as a chemical catalyst accelerating the disproportionation of H 2 O 2 into H 2 O and O 2 during the ORR process at GCEs. In alkaline media, Wang et al [5] have reported that partial reduction of hematite nanoplates activate them as electrocatalysts for ORR and that magnetite (Fe 3 O 4 ) plus hematite composites offer the higher catalytic performance. The "chemical" catalytic cycle for ORR [4] is schematized in Figure 3a.…”

“…[1] Among other compounds, hematite (α-Fe 2 O 3 ) has claimed attention as a photoanode for producing the oxygen evolution reaction (OER) because of its low cost, stability in contact with alkaline solutions, n-type semiconducting properties and band gap of around 2.0 eV. Processes catalyzed by hematite include oxygen reduction reaction (ORR), [2][3][4][5] photoelectrochemical water splitting, [6][7][8][9][10][11] and hydrogen peroxide oxidation. [12] The electrochemistry of hematite has been widely studied.…”

Metal–Organic Framework‐Derived Hollow CoSx Nanoarray Coupled with NiFe Layered Double Hydroxides as Efficient Bifunctional Electrocatalyst for Overall Water Splitting

“…[22,23] Consequently, numerous research groups have attempted to develop MOF-derived hollow-structured materials as highly efficient electrocatalysts for the HER process. [24,25] For example, Wang et al fabricated a Ni-Co bimetallic sulfide catalyst with a multi-shell hollow structure (derived from the MOF component of the catalyst) for enhanced HER For effective hydrogen production by water splitting, it is essential to develop earth-abundant, highly efficient, and durable electrocatalysts. Herein, the authors report a bifunctional electrocatalyst composed of hollow CoS x and Ni-Fe based layered double hydroxide (NiFe LDH) nanosheets for efficient overall water splitting (OWS).…”

Recent advances in material design and reactor engineering for electrocatalytic ambient nitrogen fixation

“…The advanced catalysts for efficiently promoting the N 2 fixation performance are discussed in this section (Table 1). 82–146 Given that the reaction potential range of the NRR overlaps with that of the HER and it has a higher kinetic barrier in comparison, most of the catalysts reported thus far are dominated by the competitive HER reaction under the reaction conditions. Consequently, the FE for the production of NH 3 is often less than 20% and the NH 3 yield is also 2–3 orders of magnitude lower than that of industrial catalysts.…”