This text describes the data presented in the paper:  Nickel Nanoparticles for Enhancing Carbon Capture

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Introductory information
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Files included in the data deposit (include a short description of what data are contained): 

1)Figure 1b: particle size distribution of nickel NiNPs determined by HRTEM.
2)Figure 2: a) pH changes when 100% CO2-Air mixture is bubbled in DI water and 30ppm NiNPs suspension, b) pH changes when 12% CO2-Air mixture is bubbled in DI water and 30ppm NiNPs suspension, c) pH change when 12% and 100% CO2 is bubbled in 30 ppm NiNPs suspension and d) pH change when 12% and 100% CO2 is bubbled in DI water. 
3)Figure 3: : pH dependent hydration of CO2 in presence of NiNPs at different pH a) at pH 7 using Bis-Tris-HCl buffer and b) at pH 11.5 using sodium carbonate solution.
4)Figure 4: Change in pH of DI water (square) or NiNPs suspension (circle) when CO2 is bubbled through liquid maintained at temperatures (a) 10 °C, (b) 20 °C, (c) 30 °C, (d) 40 °C, (e) 50 °C and (f) 60 °C.
5)Figure 5: Increase in weight of 50 wt% K2CO3 solution with and without NiNPs when CO2 is bubbled in it. 
6)Figure 8: pH changes during bubbling of CO2 through DI water (a) heat treated NiNPs (at 150 °C for 8 hours in air) suspension and (b) without heat treatment.
7)Figure 9: CaCO3 precipitate obtained in DI water and NiNPs suspension after CO2 bubbling at different time intervals. 



Explain the relationship between multiple data sets, if required
All data are in a set of two. The data is data is labled for DI water and NiNPs respectively


Key words used to describe the data:

Ni nanoparticles, catalysis, hydration of CO2, carbonate absorption, CO2 mineralization, pH dependence, temperature dependence.

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Methodological information
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A brief method description – what the data is, how and why it was collected or created, and how it was processed:

The NiNPs are bought from NanoTechnology, Korea. Sodium hydroxide, calcium chloride, potassium carbonate, sodium carbonate, Bis-Tris buffer and concentrated HCl (analytical grade) are purchased from Sigma Aldrich, UK. 99% CO2 and 12% CO2-air synthetic gas was bought from BOC. 18.2 MO/cm resistivity water was used for all experiments obtained from Nanopure Barnstead UK. 
The Bis-Tris-HCl buffer was prepared by mixing the Bis-Tris buffer in DI water (0.1M). The pH of the buffer was adjusted by adding drop by drop of concentrated HCl. 0.1M Na2CO3 solution was also prepared by mixing Na2CO3 in DI water. Saturated solution was made by bubbling CO¬2 in DI water for 4 hours until it saturates. The procedure for qualitative kinetic analysis was carried out by the procedure described by Mirjafari et al [29]. 20 ml of Bis-Tris-HCl buffer (or Na2CO3 solution 0.1M) was taken in a 50 ml beaker. The pH of the solution was monitored using HI2500 pH meter (Hanna Instruments) in Log mode with data logging after every 5 sec. After 5 stable readings logged in the pH log, 20 ml of saturated CO2 solution was added to the Bis-Tris-HCl buffer (or Na2CO3 solution 0.1M). The pH was recorded until a stable reading was observed. For the NiNPs catalyst run, 30 ppm suspension of Bis-Tris-HCl buffer (or Na2CO3 solution) was prepared and the above process was repeated for this solution. The experiment was performed three times and the average of the results are presented.
The CO2 hydration kinetics experiment was performed similar to the method used by Bhaduri and Šiller [9]. The CO2 hydration rate was carried out in a 250 ml glass jar within a fixed volume (200 ml) of DI water (or 30 ppm NiNPs suspension). The CO2 gas was sparged into the solution at a flow rate of 50 ml/min at 0.1MPa pressure using a glass sinter (Pyrex 1, Sigma Aldrich, UK). The pH changes of the solution are monitored during the bubbling experiments using a HI2550 pH meter (Hanna Instruments). The readings were at an interval of 20 seconds. The temperature of the sample was maintained by immersing the glass jar in a water bath (BS5, Fisher Scientific) at different temperatures (i.e. 10°C, 20°C, 30°C, 40°C, 50°C and 60°C respectively). The same experiment with 12% CO2-air synthetic gas 20°C is repeated five times and their average results are presented.
The CaCO3 precipitation experiments were carried out using the following methodology. 100 ml of DI water (or 30 ppm NiNPs suspension) was taken in a 150 ml glass jar and was bubbled with CO2 with a flow rate of 1.96 mM/min, at 0.1MPa pressure different time intervals (i.e. 0.5 hr, 1 hr, 2 hrs and 4 hrs respectively). To the respective CO2 saturated samples were added 10 ml of 1 M NaOH solution and 10 ml of 1 M CaCl2 solution. The samples were stirred and the calcium carbonate was allowed to precipitate in the glass jar. The precipitates are filtered using a vacuum filter using a Watman 54, air dried at 60°C for 1 hour and then weighted. The CaCO3 precipitated in the presence of NiNPs were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) for shape and structural determination. All experiments have been repeated three times and average data is presented.
To study the influence of NiNPs on the absorption rate of CO2 in K2CO3 solutions, the 50% (by weight) K2CO3 solution was prepared in 50 ml DI water. For the NiNPs suspension-K2CO3 solution, 1.5 mg of NiNPs was added into 50% K2CO3 solution and sonicated in the ultrasonic bath at constant temperature to make a 30 ppm solution. The concentration of 30 ppm was selected based on our previous studies [9]. The CO2 absorption experiment are performed in a 180 ml glass jar (Wheaton Industries, UK). The solution with the glass bubbler (Pyrex 1) was assembled and weighed before the introduction of CO2. The CO2 gas was bubbled at a flow rate of 1.69 mM/min at a pressure of 0.1 MPa. The final weight was obtained when there was no further possibility of gas flow though the bubbler. The gas bubbler was blocked by the formation of potassium bicarbonate crystals on the glass bubbler. The entire absorption experiment was carried out at 20 °C using a water bath (BS5, Fisher Scientific). All the above experiments were carried out in triplets and an average data is presented.
For the heat treatment, the NiNPs were placed in a silica crucible and heated in an oven at 150 °C for 8 hours. The CO2 hydration catalysis using the heat treated NiNPs was carried out using the same methodology used for temperature dependent kinetics mentioned above. CO2 catalysis was carried out for the heat treated NiNPs using same methodology as Bhaduri and Šiller [9] at room temperature and atmospheric pressure. The kinetic analysis of the heat treated NiNPs and DI water was carried out in triplets and average data is presented. 


Instruments, hardware and software used: 

pH meter (HI2550), Water bath (BS 5 Fisher Scientific), Origin 6 for regression analysis

Date(s) of data collection: 

between June 2012-August 2014

Geographic coverage of data:

Newcastle University, Newcsatle upon Tyne, UK

Data validation (how was the data checked, proofed and cleaned):

All data was used as generated. 

Overview of secondary data, if used:

N/A

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Data-specific information
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Definitions of names, labels, acronyms or specialist terminology uses for variables, records and their values: 

DI Water: Deionised water
NiNPs: Nickel Nanoparticle suspension in water (30 ppm concentration)

Explanation of weighting and grossing variables: 

N/A

Outline any missing data:

N/A

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Contact
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Please contact rdm@ncl.ac.uk for further information