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Near-infrared-driven decomposition of metal precursors yields amorphous electrocatalytic films.

Salvatore DA, Dettelbach KE, Hudkins JR, Berlinguette CP - Sci Adv (2015)

Bottom Line: Amorphous metal-based films lacking long-range atomic order have found utility in applications ranging from electronics applications to heterogeneous catalysis.We introduce herein a scalable preparative method for accessing oxidized and reduced phases of amorphous films that involves the efficient decomposition of molecular precursors, including simple metal salts, by exposure to near-infrared (NIR) radiation.The NIR-driven decomposition process provides sufficient localized heating to trigger the liberation of the ligand from solution-deposited precursors on substrates, but insufficient thermal energy to form crystalline phases.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, British Columbia V6T1Z3, Canada.

ABSTRACT
Amorphous metal-based films lacking long-range atomic order have found utility in applications ranging from electronics applications to heterogeneous catalysis. Notwithstanding, there is a limited set of fabrication methods available for making amorphous films, particularly in the absence of a conducting substrate. We introduce herein a scalable preparative method for accessing oxidized and reduced phases of amorphous films that involves the efficient decomposition of molecular precursors, including simple metal salts, by exposure to near-infrared (NIR) radiation. The NIR-driven decomposition process provides sufficient localized heating to trigger the liberation of the ligand from solution-deposited precursors on substrates, but insufficient thermal energy to form crystalline phases. This method provides access to state-of-the-art electrocatalyst films, as demonstrated herein for the electrolysis of water, and extends the scope of usable substrates to include nonconducting and temperature-sensitive platforms.

No MeSH data available.


Related in: MedlinePlus

Cyclic voltammograms for a-FeOx and a-Fe.(A and B) Cyclic voltammograms for thin films of (A) a-FeOx and (B) a-Fe on FTO. Values indicate the sequence of the cycles that were recorded. (A) The oxidative sweep of a-FeOx leads to a sharp rise in current coincident with catalytic water oxidation, and subsequent cycles led to superimposable traces. (B) The oxidative sweep for a-Fe featured a markedly different current profile for the first cycle; however, subsequent cycles indicated that a-Fe was converted to a-FeOx upon oxidation on the basis of the superimposable scans. The differences in the reductive behavior were more stark, and the cathodic peak at −0.25 V for (A) a-FeOx was not detected for (B) a-Fe before HER catalysis, indicating a more reduced form of iron for (B). Experimental conditions: counter electrode = Pt mesh; reference electrode = Ag/AgCl, KCl (sat’d); scan rate = 10 mV s−1; electrolyte = 0.1 M KOH (aq).
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Figure 2: Cyclic voltammograms for a-FeOx and a-Fe.(A and B) Cyclic voltammograms for thin films of (A) a-FeOx and (B) a-Fe on FTO. Values indicate the sequence of the cycles that were recorded. (A) The oxidative sweep of a-FeOx leads to a sharp rise in current coincident with catalytic water oxidation, and subsequent cycles led to superimposable traces. (B) The oxidative sweep for a-Fe featured a markedly different current profile for the first cycle; however, subsequent cycles indicated that a-Fe was converted to a-FeOx upon oxidation on the basis of the superimposable scans. The differences in the reductive behavior were more stark, and the cathodic peak at −0.25 V for (A) a-FeOx was not detected for (B) a-Fe before HER catalysis, indicating a more reduced form of iron for (B). Experimental conditions: counter electrode = Pt mesh; reference electrode = Ag/AgCl, KCl (sat’d); scan rate = 10 mV s−1; electrolyte = 0.1 M KOH (aq).

Mentions: The formation of amorphous metal oxide films upon exposure of metal salts to NIR radiation was confirmed by placing FeCl3 spin-cast on FTO, FeCl3/FTO, under a 175-W NIR lamp for 120 min in an aerobic environment. The color change from yellow to light brown upon irradiation supported the formation of iron oxide (UV-vis spectra are provided in fig. S2), whereas the absence of reflections in the powder x-ray diffraction (XRD) patterns indicated the amorphous nature of the material (figs. S3 and S4). (A signature Bragg reflection of hematite is apparent at 2θ = 35.9° only after annealing the same film in air for 1 hour at 600°C.) The electrochemical behavior of this amorphous film, a-FeOx, in aqueous media was also consistent with previous accounts of amorphous iron oxide (Fig. 2 and Table 1). These films demonstrated oxidative stability at a current density of 10 mA/cm2 over a 2-hour period (fig. S5). An extensive electrochemical analysis indicated that a-FeOx could be readily produced from other iron compounds [for example, Fe(NO3)3 and Fe(eh)3; eh = 2-ethylhexanoate] (fig. S6) and that the NIRDD method translated effectively to other metals: Films of a-IrOx, a-NiOx, and a-MnOx were also formed when the corresponding metal compounds were subjected to NIR radiation (figs. S7 and S8). The electrocatalytic properties of a-IrOx in 1 M H2SO4 (fig. S8) are consonant with literature values, as are those for a-NiOx and a-MnOx in alkaline conditions (Table 1).


Near-infrared-driven decomposition of metal precursors yields amorphous electrocatalytic films.

Salvatore DA, Dettelbach KE, Hudkins JR, Berlinguette CP - Sci Adv (2015)

Cyclic voltammograms for a-FeOx and a-Fe.(A and B) Cyclic voltammograms for thin films of (A) a-FeOx and (B) a-Fe on FTO. Values indicate the sequence of the cycles that were recorded. (A) The oxidative sweep of a-FeOx leads to a sharp rise in current coincident with catalytic water oxidation, and subsequent cycles led to superimposable traces. (B) The oxidative sweep for a-Fe featured a markedly different current profile for the first cycle; however, subsequent cycles indicated that a-Fe was converted to a-FeOx upon oxidation on the basis of the superimposable scans. The differences in the reductive behavior were more stark, and the cathodic peak at −0.25 V for (A) a-FeOx was not detected for (B) a-Fe before HER catalysis, indicating a more reduced form of iron for (B). Experimental conditions: counter electrode = Pt mesh; reference electrode = Ag/AgCl, KCl (sat’d); scan rate = 10 mV s−1; electrolyte = 0.1 M KOH (aq).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643823&req=5

Figure 2: Cyclic voltammograms for a-FeOx and a-Fe.(A and B) Cyclic voltammograms for thin films of (A) a-FeOx and (B) a-Fe on FTO. Values indicate the sequence of the cycles that were recorded. (A) The oxidative sweep of a-FeOx leads to a sharp rise in current coincident with catalytic water oxidation, and subsequent cycles led to superimposable traces. (B) The oxidative sweep for a-Fe featured a markedly different current profile for the first cycle; however, subsequent cycles indicated that a-Fe was converted to a-FeOx upon oxidation on the basis of the superimposable scans. The differences in the reductive behavior were more stark, and the cathodic peak at −0.25 V for (A) a-FeOx was not detected for (B) a-Fe before HER catalysis, indicating a more reduced form of iron for (B). Experimental conditions: counter electrode = Pt mesh; reference electrode = Ag/AgCl, KCl (sat’d); scan rate = 10 mV s−1; electrolyte = 0.1 M KOH (aq).
Mentions: The formation of amorphous metal oxide films upon exposure of metal salts to NIR radiation was confirmed by placing FeCl3 spin-cast on FTO, FeCl3/FTO, under a 175-W NIR lamp for 120 min in an aerobic environment. The color change from yellow to light brown upon irradiation supported the formation of iron oxide (UV-vis spectra are provided in fig. S2), whereas the absence of reflections in the powder x-ray diffraction (XRD) patterns indicated the amorphous nature of the material (figs. S3 and S4). (A signature Bragg reflection of hematite is apparent at 2θ = 35.9° only after annealing the same film in air for 1 hour at 600°C.) The electrochemical behavior of this amorphous film, a-FeOx, in aqueous media was also consistent with previous accounts of amorphous iron oxide (Fig. 2 and Table 1). These films demonstrated oxidative stability at a current density of 10 mA/cm2 over a 2-hour period (fig. S5). An extensive electrochemical analysis indicated that a-FeOx could be readily produced from other iron compounds [for example, Fe(NO3)3 and Fe(eh)3; eh = 2-ethylhexanoate] (fig. S6) and that the NIRDD method translated effectively to other metals: Films of a-IrOx, a-NiOx, and a-MnOx were also formed when the corresponding metal compounds were subjected to NIR radiation (figs. S7 and S8). The electrocatalytic properties of a-IrOx in 1 M H2SO4 (fig. S8) are consonant with literature values, as are those for a-NiOx and a-MnOx in alkaline conditions (Table 1).

Bottom Line: Amorphous metal-based films lacking long-range atomic order have found utility in applications ranging from electronics applications to heterogeneous catalysis.We introduce herein a scalable preparative method for accessing oxidized and reduced phases of amorphous films that involves the efficient decomposition of molecular precursors, including simple metal salts, by exposure to near-infrared (NIR) radiation.The NIR-driven decomposition process provides sufficient localized heating to trigger the liberation of the ligand from solution-deposited precursors on substrates, but insufficient thermal energy to form crystalline phases.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, British Columbia V6T1Z3, Canada.

ABSTRACT
Amorphous metal-based films lacking long-range atomic order have found utility in applications ranging from electronics applications to heterogeneous catalysis. Notwithstanding, there is a limited set of fabrication methods available for making amorphous films, particularly in the absence of a conducting substrate. We introduce herein a scalable preparative method for accessing oxidized and reduced phases of amorphous films that involves the efficient decomposition of molecular precursors, including simple metal salts, by exposure to near-infrared (NIR) radiation. The NIR-driven decomposition process provides sufficient localized heating to trigger the liberation of the ligand from solution-deposited precursors on substrates, but insufficient thermal energy to form crystalline phases. This method provides access to state-of-the-art electrocatalyst films, as demonstrated herein for the electrolysis of water, and extends the scope of usable substrates to include nonconducting and temperature-sensitive platforms.

No MeSH data available.


Related in: MedlinePlus