Supporting information Nickel Oxide Reduction by Hydrogen: Kinetics ...
Supporting information
Nickel Oxide Reduction by Hydrogen: Kinetics and Structural Transformations
Khachatur V. Manukyan1,2 Arpi G. Avetisyan2, Christopher E. Shuck3, Hakob A. Chatilyan2, Sergei Rouvimov4, Suren L. Kharatyan2,5, Alexander S. Mukasyan3 1
Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States 2
3
4
Laboratory of Kinetics of SHS processes, Institute of Chemical Physics NAS of Armenia, Yerevan, 0014, Armenia
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana, 46556, United States 5
Department of Chemistry, Yerevan State University, Yerevan, 0025, Armenia
1
Experimental technique for temperature measurements For experiments above 1000 K, a high-speed solar cell-based temperature sensor was applied to measure the temperature. Below 1000 K, a reference platinum wire with the same geometry is used to calibrate the electrical power needed to heat NiO/Ni samples to the desired temperatures. During calibration, platinum wires are heated with defined electrical power using identical conditions to determine the temperature by stationary equation of heat balance: T=To+P/h
(1)
where P is the electrical power on the wire (which is automatically kept constant); T is the temperature of the heated wire; h is heat emission (transfer) coefficient, which doesn't depend on wire composition; To is the ambient gas temperature (20oC). To determine h of the heated platinum wire, the electrical resistivity (R) was measured first and following equation1 for platinum was used to determine the temperature: T=3.01(R/R20)3 – 5.4756 (R/R20)2 + 282(R/R20) – 260.8
(2)
where R20 is the resistivity of the platinum wire at room temperature. Obtained temperature values were used to calculate h for the platinum wire with the corresponding power values by equation (1). The determined coefficients were then used to calculate the Ni wire temperatures, which were heated with the same electrical power values using equation (1). [1] Tables of Physical Constants, Handbook. I.K. Kikoin Edition, AtomIzdat, Мoscow, 1977.
2
A
B
Ni 20 µm
NiO
20 µm
Supporting Figure 1: Microstructures of Ni (A) and NiO/Ni (B) wires: the cross sections of wires are inserted.
3
H2
Supporting Figure 2: The scheme of experimental setup: high-speed solar cell-based temperature sensors (1), gas pressure sensor (2), vacuum pump (3), electronic control unit (4), reaction chamber (5), PC (6) and NiO/Ni sample (7).
4
Supporting Figure 3: Temperature – time profile of a typical experiment with heating (A) and cooling (B) stages
5
A
B
C
D
E
F
Supporting Figure 4: SEM images of sequential “Slice and View” analysis of NiO/Ni wire heated at 608 K showing distribution of pores (blue). The distance between slices is 10 nm. The arrow shows the grain boundary.
6
Supporting Table 1 Induction time depending on temperature and hydrogen pressure
Temperature, K 543 608 608 773
Pressure, kPa 6.67 6.67 1.33 6.67
Induction time, s 2000 180 1200 150
7
Nickel Oxide Reduction by Hydrogen: Kinetics and Structural Transformations
Khachatur V. Manukyan1,2 Arpi G. Avetisyan2, Christopher E. Shuck3, Hakob A. Chatilyan2, Sergei Rouvimov4, Suren L. Kharatyan2,5, Alexander S. Mukasyan3 1
Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States 2
3
4
Laboratory of Kinetics of SHS processes, Institute of Chemical Physics NAS of Armenia, Yerevan, 0014, Armenia
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana, 46556, United States 5
Department of Chemistry, Yerevan State University, Yerevan, 0025, Armenia
1
Experimental technique for temperature measurements For experiments above 1000 K, a high-speed solar cell-based temperature sensor was applied to measure the temperature. Below 1000 K, a reference platinum wire with the same geometry is used to calibrate the electrical power needed to heat NiO/Ni samples to the desired temperatures. During calibration, platinum wires are heated with defined electrical power using identical conditions to determine the temperature by stationary equation of heat balance: T=To+P/h
(1)
where P is the electrical power on the wire (which is automatically kept constant); T is the temperature of the heated wire; h is heat emission (transfer) coefficient, which doesn't depend on wire composition; To is the ambient gas temperature (20oC). To determine h of the heated platinum wire, the electrical resistivity (R) was measured first and following equation1 for platinum was used to determine the temperature: T=3.01(R/R20)3 – 5.4756 (R/R20)2 + 282(R/R20) – 260.8
(2)
where R20 is the resistivity of the platinum wire at room temperature. Obtained temperature values were used to calculate h for the platinum wire with the corresponding power values by equation (1). The determined coefficients were then used to calculate the Ni wire temperatures, which were heated with the same electrical power values using equation (1). [1] Tables of Physical Constants, Handbook. I.K. Kikoin Edition, AtomIzdat, Мoscow, 1977.
2
A
B
Ni 20 µm
NiO
20 µm
Supporting Figure 1: Microstructures of Ni (A) and NiO/Ni (B) wires: the cross sections of wires are inserted.
3
H2
Supporting Figure 2: The scheme of experimental setup: high-speed solar cell-based temperature sensors (1), gas pressure sensor (2), vacuum pump (3), electronic control unit (4), reaction chamber (5), PC (6) and NiO/Ni sample (7).
4
Supporting Figure 3: Temperature – time profile of a typical experiment with heating (A) and cooling (B) stages
5
A
B
C
D
E
F
Supporting Figure 4: SEM images of sequential “Slice and View” analysis of NiO/Ni wire heated at 608 K showing distribution of pores (blue). The distance between slices is 10 nm. The arrow shows the grain boundary.
6
Supporting Table 1 Induction time depending on temperature and hydrogen pressure
Temperature, K 543 608 608 773
Pressure, kPa 6.67 6.67 1.33 6.67
Induction time, s 2000 180 1200 150
7
