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FeN(Pt,Cu)/defBN and CoN(Pt,Cu)/defBN powders

Index

How balls/h-BN ratio of hBN ball-mill treatment influence characteristics of FeN/h-BN?

Samples were produced via Fe hydroxide chemical precipitation. Boron nitride powder was dispersed in acidified iron nitrate solution using ultrasound at 5°C. NaOH water solution was added to the suspension dropwise at 5°C at vigorous stirring using magnetic mixer. After deposition, samples were washed with water and dried in IPA at ambient conditions. Nitrides were obtained via ammonolysis in ammonia flow at 500°C.

XRD

Samples consist of h-BN, Fe2N and Fe3O4 phases. There is no change in composition depending on b/s ratio. The difference is only in FWHM of h-BN peaks.

SEM

Samples consist of particles with size < 100 nm on the surface of h-BN. The increase of b/s ratio leads to decrease of particles size and their uniform distribution on the surface of hBN.

dl109: no mill dl121: b/s=22 dl122: b/s=33 dl126: b/s=44 dl123: b/s=51
EDX

Samples contain B, N, Fe, O elements and up to 0.5 at.% Si impurity. There are homogeniously formed iron nitride particles in sample on BN without ball-milling treatment. In case of ball-milled samples, iron is distributed uniformly among particles.

B
N
Fe
O
Si
dl109: no mill dl121: b/s=22 dl122: b/s=33 dl126: b/s=44 dl123: b/s=51
BET

Specific surface area decreases after metal nitride deposition. It is still higher 150 m2/g for ball-milled samples.

Sample b/s ratio Ssp Ssp,sup
m2/g m2/g
dl109 no mill 4.787 28.726
dl121 22 196.815 309.173
dl122 33 198.621 320.71
dl126 44 167.740 248.579
dl123 51 230.428 224.79
CO2 hydrogenation

CO2 conversion is higher for sample, produced without ball-milling treatment. Selectivity to hydrocarbons is highest for sample with BN ball-milled at 22 b/s ratio at 200°C. However it is highest for non-milled sample at 380°C.

How does composition of active phase (Co-N, Fe-N, Co, Fe) and type of defects (vacancies/amorphisation and C substitution) of BN support influences characteristics of resulting catalysts?

Samples were produced using method with Co (II) and Fe (III) nitrate salts. BN ball-milled with mass of balls to mass of BN equal 51 ratio and the one, ball-milled with D-Glucosamine HCl were used as support materials. These where chosen to have as close specific surface area as possible.

CHNS
Sample C content, wt.%
BN 0.44
dl124: BCN 3.80
BET

Sample Ssp, m2/g
dl202: BN 29
dl116: defBN 225
dl124: BCN 214

XRD

FTIR

NMR

XPS

B1s N1s

Sample B1s N1s
BN BNO BO BN BNO BNH
dl202: BN 74.82 25.18 - 69.74 27.58 2.68
dl116: defBN 65.50 21.96 12.54 65.81 25.23 8.96
dl124: BCN 62.10 29.00 8.90 65.00 23.88 11.11

Sample B N O C Fe/Co
dl123:FeN/BN 45.03 34.38 14.68 5.16 0.75
dl132:CoN/BN 47.29 37.52 10.32 4.15 0.71
dl130:FeN/BCN 43.61 38.52 8.61 9.01 0.26
dl131:CoN/BCN 45.76 39.57 7.85 6.14 0.68

Sample B 1s N 1s Fe 2p Co 2p
BN BNO BO BN BNO BNH BCN FeN Fe(2+) Fe(3+) CoN Co(2+) Co(3+)
dl123:FeN/BN 43.39 46.17 10.44 49.17 47.91 2.93 3.71 72.93 23.36
dl132:CoN/BN 49.17 46.39 4.44 55.67 41.27 3.06 12.56 52.88 34.56
dl130:FeN/BCN 56.50 37.17 6.32 65.96 32.01 2.03 14.55 63.87 21.58
dl131:CoN/BCN 51.18 41.07 7.75 53.88 40.41 4.47 1.24 14.94 58.03 27.03

SEM

Cobalt nitride particles are smaller compared to Fe-N counterpart. Particles tend to concentrate in islands. There is no noticeable difference between BN and BCN supported particles.

dl123: FeN/BN dl132: CoN/BN dl130: FeN/BCN dl131: CoN/BCN
EDX

Elemental maps show that Co-N is more uniformly distributed over support surface. There is no Si impurity in samples, produced using BCN support.

B
N
Fe/Co
O
Si
dl123: FeN/BN dl132: CoN/BN dl130: FeN/BCN dl131: CoN/BCN
TEM
dl123: FeN/BN dl132: CoN/BN dl130: FeN/BCN dl131: CoN/BCN
Size distribution
HAADF TEM EDX
Fe/Co
N
B
C
O
dl123: FeN/BN dl132: CoN/BN dl130: FeN/BCN dl131: CoN/BCN
CO2 hydrogenation

Co based catalysts are more active in comparison to Fe based ones. Also, Co-based catalysts posesses higher selectivity towards hydrocarbons. Among Fe-based catalysts, conversion decreases in the order Fe-N/BCN > Fe-N/BN > Fe/BCN. Selectivity towards hydrocarbons for these series is not changed substantially with temperature increase, although it shifts towards lower molecular weight hydrocarbons. Preferred product for Fe-based catalysts is CO. In case of Co-based catalysts covnersion decreases in the order Co-N/BCN > Co-N/BN > Co/BCN. Selectivity towards hydrocarbons is slightly higher for Co-N/BN sample at 200°C while it is highest for Co-N/BCN sample at 380°C. There is also shift towards lower molecular weight hydrocarbons with temperature increase for this series. Preferred product for Co-based catalysts is methane.

TPD

CO2