Data underlying the PhD dissertation: Investigating the influence of a thin copper film coated on nickel plates through physical vapor deposition for electrocatalytic nitrate reduction
by: Sumit Maya Moreshwar Meshram
Experimental techniques:
Materials 
Potassium nitrate (KNO3) and sodium sulphate (Na2SO4) were used to prepare the anolyte and catholyte. Pure Cu powder with a particle size <425 ?m, density of Cu = 8.930, Z-ratio = 0.437, and 99.5% purity was utilized for the deposition on Ni plates. These Ni plates served as substrates for the Cu films coating, which functioned as the cathodes in the analysis. Platinum mesh was used as anode. All solutions were prepared using milliQ water (water obtained from a Millipore system). pH of the solution was measured using a Multi9420 InoLab IDS multimeter. 
Synthesis of thin films of Cu on Ni plate using physical vapor deposition
Nickel (Ni) plate (purity = 99.96%, thickness = 0.2 mm, Haoxuan Metal Materials Ltd)  was sanded and polished with sandpaper of grit size 4002000. To remove impurities, the Ni plate was ultrasonically degreased and cleaned in acetone and ethanol for 15 min. They were then immersed in a 1 mol.L?1 aqueous hydrochloric acid (HCl) solution for 5 min and washed with milliQ water.
Then Copper (Cu) was deposited in layer of 25,50, and 100 nm thickness on both sides of Ni plate using Physical vapour deposition (PVD) (VCM 600-SP3, rack-type vacuum evaporator) method by applying a current of ?80 A. The operation details of the PVD are: substrate temperature = 1,6001,800C, evaporation rate = 0.5 /s, current intensity = 150 Amp, base pressure = 2.8  10?7 mbar, and vacuum of 5.0  10?6 mbar was achieved. The PVD was kept under vacuum conditions, which resulted in the formation of a uniform and cohesive layer of Cu on Ni plate (Cu-Ni). Then  the CuNi was dried in air at room temperature and then the Cu-Ni sheet of 2 cm  1 cm was cut for further analysis.
Electrochemical techniques
The nitrate (NO3-) electrochemical reduction experiments were carried out using a three-electrode system in a 300 mL dual-chamber H-type reactor. The anolyte was 3.5 mM Na2SO4, whereas the catholyte consisted of 2.5 mM KNO3 and 0.5 g/L of Na2SO4 solution. 300 mL of catholyte was placed in the cathode chamber, which was then sparged with N2 gas to remove oxygen from the solution to create anaerobic conditions. A Pt mesh (1 cm  1 cm) was used as the counter (anode) electrode. A Cu-Ni plate (2 cm  1 cm) was cut from a large Cu-Ni plate and used as the working electrode (cathode). The surface area of the working electrode was 4 cm2. Ag/AgCl (3 M KCl) was used as the reference electrode. A titanium wire was connected to the Cu-Ni plate to form an external connection with the potentiostat (Admiral instruments Squidstat Prime). A proton exchange membrane (Nafion 117) was used to separate anode and cathode chambers. A gas bag was attached to the anode and cathode chamber to collect any produced gases like H2. All electrochemical experiments were performed by applying a constant current of ?8.5 mA for 6 h. Approximately 10 mL of the solution was removed between two sampling points to determine the concentrations of NO3-, NO2-, and NH4+ ions and was replaced with fresh catholyte solution. NO3-, NO2-, and NH4+ in the solutions were measured using standard Hach kits with a UV-visible spectrophotometer (DR-3900, Lange). Cyclic voltammetry (CV) was performed at a potential scan rate of 1 mV/s under two conditions: with stirring at 500 rotation per minute (rpm) and without stirring.
Cyclic voltammetry (CV)
To assess the electrocatalytic performance of Cu deposition of different thicknesses on Ni plates, CV experiments were conducted. The CV curves were obtained for various concentrations of KNO3 and Na2SO4 electrolyte solutions in the range of ?1.8 to ?0.4 V (versus Ag/AgCl (3 M KCl) reference electrode) at a scan rate of 1 mV/s.
NO3?, NO2?, and NH4+ measurement
Spectrophotometer (model number: DR3900) was employed for determining the concentration of NO3?, NO2?, and NH4+. The LCK 340, LCK 342, and LCK (303 and 304) Hach kits were utilized for measuring NO3?, NO2?, and NH4+, , respectively.
Scanning Electron Microscopy (SEM)
Field emission scanning electron microscope (FE-SEM, JEOL JSM 6500F), which was equipped with an EDX detector. 
X-ray Photoelectron Spectroscopy (XPS)
The surface chemistry of the samples was analyzed using a PHI-TFA XPS spectrometer from Physical Electronic Inc., which featured an Al K? X-ray monochromatic source (hv = 1486.7 eV). The pass energy for the survey was set at 89.45 eV, and a vacuum of approximately 109 mbar was maintained during the XPS analysis (Cornet et al., 2024). Data was analyzed using Multipak version 8.0 software. Peaks were normalized and fitted using the iterated-Shirley background method
Product Analysis
Product analysis was conducted using three-electrode system in 300 mL dual-chamber H-type reactor (Adams & Chittenden Scientific Glass Coop), connected to a Squidstat 4 channel potentiostat. The anode compartment contained a platinum wire serving as the counter electrode. The cathode compartment included the working electrode, Cu-Ni (25 nm, 50 nm, and 100 nm), and 3M KCl, AG/AgCl electrode was used as reference electrode. 
The conversion rate [C[NO_3^- ]%] of NO3?was calculated usingfollowing equation
C[NO_3^- ]%={C_0 [?NO?_3^--N]-C_t [?NO?_3^--N]}/(C_0 [?NO?_3^--N] )100%
The selectivity [S[NH4+]%] ofNH4+can be calculated usingfollowing equation

S[NH_4^+ ]%={C_t [NH_4^+-N]}/(C_0 [?NO?_3^--N]- C_t [?NO?_3^--N] )100%
The concentration of gaseous compounds was calculated using following mass balanceequation
C[Gaseous compounds]=C_0 [?NO?_3^--N]- ?(C?_(nitrate remaining in solution)+C_nitrite+C_ammonium)
where,
C0 (NO3?N)is initial the concentration ofNO3?-N(mg/l), 
V is the volume of the electrolyte in the cathode compartment (L), where subscript 0 represents the initial condition whereas t represents the condition after time t.

Data files

CV data files
NO3?, NO2?, and NH4+, Concentration data files
XPS data files
LSV data files
SEM data files

