PSD and CLD. Particle size Distribution (PSD) was measured using Horiba Laser Scattering Particle Size Distribution Analyzer LA-960 equipped with a wet flow cell where 96% ethanol (refractive index of 1.3600) was used as the dispersion media. BM was carefully added to the cell until a transmittance of ~80 % was achieved for each measurement. The Refractive (R) index of pure graphite (2.000 R index and 0.5220 I index) was used as the representative R index for the whole BM sample. Chord length distribution (CLD) measurements were carried out using the Mettler Toledo ParticleTrack G400 FBRM instrument. For each measurement, the BM sample was dispersed in 96 % ethanol at a solid/liquid ratio of 2 g/L (particle counts ranging from 15000 -20000). FBRM probe was dipped in the prepared dispersion and the dispersion was stirred at 700 rpm to make sure all particles were completely wetted. For each measurement, sampling was done at a 30 sec interval for 15 minutes, and an average of all samplings was determined to represent the measurement. Digestion and metal composition analysis. Digestion of metals in BM samples was carried out using a microwave-assisted digestion instrument called Berghof Speedwave XPERT equipped with DAP-60 digestion vessels. Measurement of the metal contents (wt. %) after microwave digestion was done using a microwave plasma atomic emission spectrometry (MP-AES) instrument called Agilent MP-AES 4210. For digestion, ~100 mg of BM sample was weighed and added in the digestion vessel (without using a sample cup), followed by the addition of 1 mL of ultrapure water, 7 mL of 37 % HCl, and 3 mL of 65 % HNO3 in the same order as mentioned. The vessel was properly sealed and placed in the instrument. The temperature profile in the digestion instrument was configured so that the temperature was first increased to 180 °C and held there for 15 minutes. Further, the temperature was increased to 220 °C and held there for 30 minutes. After the digestion was done, the contents of the vessel were poured into a 50 mL volumetric flask. The digestion solution containing metallic ions was filtered using a 25 µm syringe filter and further diluted by a dilution factor of 100 using ultrapure water. The metal composition (wt. %) of the diluted solutions was determined using the MP-AES instrument. XRD. X-ray diffraction (XRD) analysis was performed on a Bruker DaVinci1 diffractometer using Cu-Kα radiation (λ=1.54060 Å) equipped with a Ni filter to reduce the intensity of the contamination wavelengths (i.e., Cu-Kβ and W-Lα). XRD experiments were carried out at a step size of 0.01°, time/step of ~1 sec, fixed divergence slit (FDS) of 0.2° and a 2θ range of 15° -60°. Zero diffraction cavity type (15 mm diameter) sample holder was used for sample preparation. BM powder was manually ground in a mortar and a certain amount was distributed over the sample holder using a glass slide. The sample was tightly packed by manually pressing from the top. The diffraction patterns were matched to the ICDD (International Centre for Diffraction Data) PDF (Powder Diffraction File) -4+ database to identify the crystalline compounds and phases. TGA/MS. TGA/MS analyses were obtained using a Netzsch STA 449C Jupiter TGA/DSC coupled with a Netzsch Aëolos QMS 403C. For TGA/MS under inert conditions, approximately 50 mg of BM sample was analyzed in an alumina crucible. The sample was first heated to 50 °C from room temperature and then held there for 3 hours. This step was done to make sure that all oxygen was completely purged from the instrument's chamber and the further heating process would essentially take place in an inert atmosphere. Argon (Ar) was used as the protective gas at a flow rate of 20 ml/min as well as the purge gas at a flow rate of 80 ml/min. In the next step, the temperature was gradually increased from 50 °C to 1000 °C at a heating rate of 5 °C/min and then kept there for 1 hour. For TGA/MS under oxidative conditions, 20 -30 mg of BM sample in an alumina crucible was first heated to 110 °C, and the temperature was held at 110 °C for 1 hour to make sure that adsorbed moisture was completely evaporated. The temperature was then increased to 1000 °C at a heating rate of 5 °C/min under 20 ml/min Ar (used as protective gas) and 100 ml/min purified air (used as the purge gas). The flow rate of the purified air (purge gas) is kept high to make sure that oxygen would not be a limiting reactant. During both conditions, the evolved gases from the TGA instruments were directed to the MS using a transfer line heated at 300 °C. The MS instrument was configured to detect the species based on their m/z (mass-tocharge) ratios (listed in Table ). The use of Ar as a protective and purge gas during inert TGA/MS analyses is essential here since the m/z value of other commonly available inert gases (e.g., N2) overlaps with the m/z values of species in the evolved gas (e.g., CO). SEM/EDS. Morphological and elemental analyses of the BM samples were obtained using an SEM Apreo instrument coupled with the EDX Oxford Xmax 80 detector. For preparation of the samples for SEM/EDS imaging, a polyester swab was dipped in the BM sample and rolled over a conductive tape. Pressurized N2 gas was used to remove any loosely bound particles, and the sample-covered conductive tape was pasted on an aluminum stub. For imaging these samples, an ETD detector was employed at a working distance of ~4 mm to obtain high-res images. A voltage of 5 -7 kV and a current of ~1.6 nA was applied. During elemental analysis using the EDX detector, the working distance was changed to 10 mm and the current was adjusted to obtain a dead time value of 40 -60 %. Raman. Raman spectroscopy of BM samples was performed using a WITec Alpha 300R instrument equipped with a 532 nm wavelength. To avoid oxidation and decomposition of carbonaceous species deposited on the surface of graphite particles in BM, a very lower laser power of 0.2 -0.5 mW was utilized. Due to the uneven sample surface (caused by the heterogeneous particle size of BM), a 50x objective with a relatively long working distance of ~9 mm was used. An optimal acquisition time and accumulations were first determined, and it was found that an acquisition time of 20 sec while keeping the number of accumulations to 10 provided consistent and repeatable measurements without damaging the surface. All measurements were taken by setting the grating at 600 g/mm and keeping the spectral center at ~2199.999 cm -1 . For deconvolution and fitting the raw Raman spectra, the Fityk peak fitting program was used. A linear function was applied to subtract the background, and the 1 st -order carbon peaks were fitted using the Lorentzian function. An R-squared value of >99 % was achieved for spectrum fitting using the Lorentzian function. The results obtained from the fitting were used to analyze spectral features (e.g., intensities of various peaks). ATR-FTIR. ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) spectroscopy measurements of evaporated species from BM3 were performed using the Bruker Vertex 80v instrument. ATR-FTIR scans were run from 500 -4000 cm -1 wavenumber range at a scan speed of 4 cm -1 .