Zeolitic Imidazole Framework Derived Cobalt Phosphide/Carbon Composite and Waste Paper Derived Porous Carbon for High‐Performance Supercapattery

Metal–organic frameworks (MOFs) derived nanostructures receive immense research focus due to its high porosity, conductivity, and structural tailrolability features. In this work, porous Zeolitic Imidazole Framework‐67 (ZIF‐67) to synthesize cobalt phosphide/carbon composite (ZCoPC) that serves as a positive electrode is utilized. Furthermore, porous and conductive office paper derived carbon (OPC) are utilized as a negative electrode to make a hybrid system. The metalloid characteristics, high conductivity, and good porosity of ZCoPC material makes it a high‐performance battery like electrode. ZCoPC electrode achieves maximum specific capacity of 192.6 mAh g−1 at 1 A g−1 using 1 m potassium hydroxide (KOH) electrolyte. Furthermore, surface and diffusion charge participation investigation are also undergone for ZCoPC electrode that helps in determining the actual charge dynamics occurring in the electrode. In addition, a supercapattery device is assembled using ZCoPC as battery electrode and OPC as supercapacitor electrode. The as fabricated OPC//ZCoPC hybrid supercapattery device delivers extraordinary energy density of 31.6 Wh kg−1 with a power density of 700 W kg−1 and also a long cycle life of 92.3% even after 10,000 charge–discharge cycles. Hence, these outcomes demonstrate that the synergy of porous MOF derived metal phosphide and OPC electrodes are beneficial for supercapattery devices.


Introduction
The need for portable electronics and the electrification of transportation has increased the demand for electrochemical energy storage devices like Li-ion batteries (LIBs) and supercapacitors DOI: 10.1002/admi.202300401(SCs). [1]Although classic carbon-based SCs perform better than alternative technologies, their industrial applications are constrained by their low energy density. [2,3][6] Supercapattery use two electrodes constructed of different materials with different mechanism for charge storage.Supercapattery, which offers a range of voltage beyond the thermodynamic breakdown of water facilitated electrolytes, typically consists of a capacitor-type negative electrode and a battery based positive electrode. [7,8]apacitor-type electrode shows fast polarization of double layer, whereas battery type electrode shows high energy density through redox activity.Pairing electrodes with optimum compatibility is the biggest obstacle in creating a highperformance supercapattery device. [9]rimarily, transition metal phosphides (TMPs), are of special interest owing to their metalloid characteristics and high electrical conductivity. [10]TMPs are faradaic battery-type materials exhibiting high specific capacities and energy density, which makes them suitable as a positive electrode in supercapattery.However, TMPs display slow ion-kinetics in the bulk due to their low specific surface areas and porosity, which limit  the access to electrochemically active sites and increases diffusion lengths. [11,12]This issue can be tackled by developing porous TMPs using metal-organic frameworks (MOFs) as template. [13]n MOF derived TMPs, the metal phosphide nanoparticles will be homogeneously distributed in a carbon network (organic linkers).The co-existence of nanocarbons with TMP facilitates the ionic conducting pathways and reduces the diffusion lengths that improves the charge transfer efficiency and also provide longterm cycling stability. [14,15]In literature, various researchers have tried to utilize MOF derived TMPs as supercapacitor electrodes.For instance, Zhang et al. used Fe-MOF derived FeP nanostructures that delivered decent energy storage performance. [16]Similarly, Xu et al. synthesized coral like Ni 2 P/C that serves as positive electrode in hybrid supercapacitor (HSC) which renders a specific capacity of 271 mAh g −1 . [17]Meanwhile, Wang's group developed an efficient sulfurization strategy to prepare S@CoP nanotubes that showed a specific capacity ≈1.8 times more than that of pristine CoP. [18]More recently, Sun et al. undergone Copper doping in Cobalt Phosphide and it achieved a specific capacity of 113.3 mAh g −1 with augmented cyclic stability and rate capability for fabricated HSCs. [19]Despite this progress, the synergy of TMPs arrays as positive electrode with commercial activated carbon negative electrode in aqueous electrolyte media is unable to achieve satisfactory electrochemical performance.
Therefore, in this work we develop a novel supercapattery by utilizing ZCoPC as battery type positive electrode and pairing them with OPC negative electrode to achieve high energy and power densities while retaining long cycle life.The ZCoPC electrode shows remarkable performance in both three and two electrode electrochemical system.In addition, the well observed surface and diffusion contributions parameters also confirms the better electroactivity of ZCoPC electrodes.Furthermore, the OPC//ZCoPC supercapattery renders the highest energy density of 31.6 Wh kg −1 with high-power density of 700 W kg −1 even in 1 m KOH aqueous electrolyte.The schematic showing the sum-mary of designing material to supercapattery device is given in Figure 1.The proposed hybrid supercapattery device with high energy and power densities along with a long-life cycle, can leads to the next generation power source for various applications.

Synthesis of ZIF-67 Derived Cobalt Phosphide/Carbon (ZCoPC)
The ZIF-67 derived cobalt phosphide/carbon composite was prepared using one-step simultaneous pyrolysis and phosphorylation technique.Briefly, the ZIF-67 synthesized from the previous work [20] and was phosphorated with SHM via high temperature pyrolysis in inert Argon atmosphere.ZIF-67 (100 mg) and 1 g of SHM were placed in a porcelain boat at two different positions with SHM at the upstream side of the tube furnace.After that the samples were annealed at 300 °C for 2 h in inert atmosphere with a ramp rate of 5 °C min −1 .The ZCoPC-1 were obtained after cooling to room temperature.Finally, the impurities and residues in the ZCoPC-1 sample were removed by stirring it in 2 m HCl overnight and washed with DI water and ethanol till the traces of acid were removed completely.After that the washed sample was dried in oven at 70 °C for 12 h in order to obtain final ZCoPC sample.

Synthesis of Office Paper Derived Porous Carbon (OPC)
Synthesis of OPC was done based on the previous published report. [21]Briefly, office papers were chopped into little pieces, dried and grinded into fine powder.Then it was pre-carbonized in 2 m H 2 SO 4 via hydrothermal approach using Teflon-lined stainless steel autoclave for 12 h at 200 °C.The pre-carbonized black material was washed filtered and then it was mixed with KOH in the ratio of 1:2.The resulted mixture was heated at 800 °C for 4 h in inert atmosphere and then the so-obtained porous carbon was washed with 2 m HCl and multiple times with DI water.The resulted material was then dried at 80 °C and denoted as OPC.

Characterization
X-ray diffractometer (Bruker D8 Advance with Cu-K source 1.54 Å) was used to record the XRD patterns of the samples.Raman spectra were taken using a Renishaw (Invia) system with a 514 nm laser source.N 2 adsorption-desorption and the BJH pore size distribution were being observed by a Quantachrome AsiQwin instrument.FESEM was used to perform morphological analysis of the samples, and to perform EDS spectroscopy and mapping (FEI Nova NanoSEM 450).Transmission electron microscopy (TEM) images were recorded on JEOL JEM-2100 TEM equipped with a LaB 6 type emission gun operating at 200 kV.FTIR was performed using Nicolet iS10 instrument.Using a Microlab 350 (Thermo Electron) spectrometer with a lateral resolution of 0.2 mm 2 and Al-K non-monochromated radiation (1486.6 eV; 300 W) as the excitation source, X-ray photoelectron spectroscopy (XPS) analysis was carried out.

Electrochemical Properties
The electrochemical performance of the as-prepared samples was assessed using cyclic voltammetry (CV), galvanostatic chargedischarge (GCD), and electrochemical impedance spectroscopy (EIS) techniques on a Biologic VMP electrochemical workstation.For casting the active electrode on current collector, a viscous slurry in NMP solvent was produced using the active material and PVDF binder in a 9:1 ratio.With a mass loading of 1.5 mg/cm 2 , the homogeneous slurry was drop-casted over a graphene foil current collector in a 1 × 1 cm 2 active region.It was then dried at 70 °C for 10 h.In a three-electrode electrochemical cell, which used platinum wire, Ag/AgCl, and working electrodes as the counter, reference, and working electrodes, respectively, the electrochemical analysis of the electrode was tested.The three-electrode electrochemical performance and surface & diffusion contribution investigations of ZCoPC electrodes were performed in 1 m KOH electrolyte.For two electrode measurements, supercapattery device were assembled and tested.For the assembling of hybrid supercapattery, ZCoPC was used as battery type positive electrode and OPC was used as negative supercapacitor electrode with the 1 m KOH electrolyte infiltrated filter paper as separator.

Equations for Electrochemical Calculations
The corresponding specific capacity for the electrode was determined from GCD curves using the equation given below: where Q represents the specific capacity (mA h/g), I represents the applied current (mA), m denotes the active material mass (g), and ∆t is discharging time.
For hybrid supercapattery device, energy density (Wh/kg) and power density (W/kg) was evaluated using the equation:

Physicochemical Characterization of ZCoPC Material
The confirmation of the formation of ZIF-67 is analyzed by XRD and FESEM analysis as shown in Figure S1a,b (Supporting Information).Furthermore, one step pyrolysis and phosphidation technique are used for the preparation of ZIF-67 derived cobalt phosphide/carbon composite.When heated at 300 °C, SHM decomposes into Na 2 HPO 4 and PH 3 gas (which helps in phosphidation).However, the decomposition by-product (Na 2 HPO 4 ) blocked the pores of cobalt phosphide/carbon (ZCoPC-1) which in turn results in poor electronic and ionic transport and hence poor energy storage performance. [22]Therefore, to improve the electrochemical activity, one additional step requires to wash these pore blockades with 2 m HCl to increase the porosity and hence overall electrochemical performance.The HCl washed product is termed as ZCoPC.Therefore, in this paper we have tried to show the thorough comparison of ZCoPC-1 and ZCoPC samples in terms of both material and electrochemical characterizations.
The prepared sample has been analyzed with XRD methods to determine the phase and crystallinity of cobalt phosphide in the material.Figure 2a shows the XRD spectra comparison of ZCoPC-1 and ZCoPC samples.For ZCoPC-1 and ZCoPC, a peak at 25.1°corresponds to the presence of carbon with (002) plane.Both ZCoPC-1 and ZCoPC consist of this carbon peak that result from the pyrolysis of organic linker which mostly consists of carbon structures.Since the pyrolysis performed in Ar atmosphere and ZIF-67 structure doesn't contain oxygen atoms, there were very less chance of any oxidation.The samples ZCoPC-1 and ZCoPC showed diffraction peaks of CoP/C at 31.8°, 35.06°, 47.4°, 51.3°, attributable to the (011), (111), (112), and (211) planes of CoP. [23]The presence of other peaks at 40.6°, 44.5°, 54.13°, 57.2°, and 74.7°are correspond to (210), ( 211), (020), (302), and (222) planes for Co 2 P. [24] Therefore, XRD confirm the presence of both phases of cobalt phosphide in the sample.
Furthermore, Raman spectra were used to gauge the extent of graphitization of carbon in the phosphidated samples.According to Figure 2b, the ordered graphitic carbon (G band) and the disordered carbon (D band) were responsible for the maxima at ≈1585 and 1350 cm −1 , respectively. [25,26]Despite not having any graphene, the phosphidated sample's distinctive Raman peaks are caused by carbon that was formed during pyrolyzing ZIF-67 precursor. [27]The degree of defects to the graphitized carbon in the samples is shown by the intensity ratio of the D to G band (I D /I G ). Since acid treatment helps to remove the defects present in the sample, the I D /I G of the ZCoPC sample is lower than the ZCoPC-1 sample, indicating that the latter sample has more defects in its carbon network.
Furthermore, the specific surface area (SSA) of the material plays important role for the adsorption and kinetics of the electrolyte ions in the material structure.The presence of mesopores is considered as the efficient pores for the adsorption, whereas the presence of macropores provide the in-depth access of the bulk material.Therefore, the presence of all the pores in a material plays critical role to achieve high capacity and rate performance.The SSA of the material has been investigated with the N 2 adsorption-desorption isotherm.Figure 2c gives the isotherm behavior comparison of both the samples that display typical type IV isotherms (mesopores) in which ZCoPC-1 and ZCoPC shows the specific surface area (SSA) of 7 and 17 m 2 g −1 , respectively.Additionally, it can be seen that the adsorption is quite low for ZCoPC-1 possibly due to the blockage of pores by decomposition by-product which can also be observed in the pore size distribution curve.However, increment in the surface area of ZCoPC can be related to the opening of the blocked pores by washing with HCl.
Basically, the ZIF-67 displayed typical type I and IV isotherms with an estimated SSA of 950 m 2 g −1 as shown in Figure S1c (Supporting Information).Furthermore, a large uptake of adsorption in the isotherm can be seen at the low pressure which is characteristic of presence of micropores in the material.Upon observing the isotherm at high pressure, one can observe a slight uptake in adsorption, which indicates the presence of macropores in the material.During electrochemical testing, these macroporous and mesoporous gaps can act as ion-buffering reservoirs.The isotherm of ZIF-67 thus confirms the presence of all type of pores in the material.
However, to further determine the quantitative distribution of pore size in the material, the BJH pore size distribution plot has been analyzed.Figure 2d shows the BJH pore size distribution comparison for both ZCoPC-1 and ZCoPC which reveals a wide peak within the range of 1 to 50 nm.The high porosity in ZCoPC sample after acid treatment promotes the fast transport of electrolyte ions.This facilitates electrolyte ions to enter the pores that helps to improve specific capacity, cycle life, energy density, and power density.The pore-size distribution plot reveals that the average pore size is in the range of mesopores, whereas a slight number of macropores can also be observed.
In addition to structural characteristics, the material's surface morphology plays a crucial role in energy storage devices since it can facilitate interactions between electrodes and electrolytes.The morphology of all the synthesized samples is determined using FESEM analysis.Figure 3a-d shows the FESEM morphological images of ZCoPC-1 and ZCoPC sample, respectively.The FESEM image of ZIF-67 showed the perfect polyhedral crystal shown in Figure S1b (Supporting Information), which gets breakdown while undergoing through thermal treatment during its conversion to phosphide.The main samples ZCoPC-1 and ZCoPC shows nanostructures of CoP/Co 2 P binds with carbon structures throughout the sample having an average diameter of ≈500 nm.In fact, both the ZCoPC-1 and ZCoPC samples consists of CoP/Co 2 P encapsulated by the matrices of pyrolyzed porous carbon.Furthermore, TEM micrographs of ZCoPC (shown in Figure 3e,f) also illustrated the encapsulation of Cobalt phosphides nanoparticles in a carbon sheath generated from ZIF-67, which contributed to the excellent stability and good electronic conductivity of ZCoPC.In addition, small nanostructure guarantees the flow of electrolytes with the high electrolyte interfacial area.The primary reason for such type of morphology is the decomposition of organic linker under high temperature pyrolysis.The carbon encapsulation with cobalt phosphide structures helps to enhance the overall porosity and conductivity of the composite which in turn helps to enhance the rapid transport of electrolyte ions and thus specific capacity of the ZCoPC positive electrode of supercapattery.
Further, the EDS and mapping confirmed the presence of cobalt phosphide and carbon atomic percentages with its dis-tribution in the material.Figure S2a (Supporting Information) shows EDS spectra of ZCoPC-1 indicating the presence of impurities, such as Na attributing to the fact that decomposition by-product (Na 2 HPO 4 ) present over the surface of ZCoPC-1.The EDS spectra in Figure S2b (Supporting Information) confirms the presence of Carbon (C), Oxygen (O), Cobalt (Co), Nitrogen (N), and Phosphorous (P) in ZCoPC with an atomic ratio of 32.9%, 30.2%, 13.3%, and 18.4, 5.2%, respectively.The elemental mapping further confirmed that Co and P elements are dispersed uniformly over the surface (Figure 3g-k).The mapping indicates the uniform distribution of CoP/Co 2 P and carbon in the structure uniformly.Therefore, during the redox conversion of CoP/Co 2 P, the electrons can be transferred to the carbon and further to the current collector very efficiently with minimum resistance losses.The EDS and mapping of the ZCoPC sample also confirmed the presence of nitrogen (N) in the sample which is coming from the organic linker of ZIF-67.The presence of N in the material also improves the electrochemical activity of the material.The N atoms restrict the aggregation of nanomaterials, as well as improves the diffusivity of electrons and ions. [28]Due to N's electronegative nature, fast electron flow between its atoms is expected to provide extra value to specific capacity. [29]Moreover, the sample included no impurity elemental peaks.The sample was predominantly composed of C, Co, P, O, and N as was to be expected.
To determine the chemical composition and bonding present in the ZCoPC sample, we performed the XPS analysis as shown in Figure 4.The XPS spectra revealed the bonding of Co, P, C, O, and N in the material.The survey scan given in Figure 4a confirms existence of Co, P, C, O, and N. Further analyzing the high-resolution spectra of Co 2p, the spectra showed two different peaks at ≈781.5 and 797.6 eV that can be assigned to the p 3/2 and p 1/2 energy level of Co as shown in Figure 4b. [19,28]Similarly, the P 2p peaks are the combination of three different peaks that corresponds to the Co─P bonds (129.6 eV) for CoP/Co 2 P and P─O (133 and 133.8 eV) due to superficial oxidation species at the surface of cobalt phosphide as shown in Figure 4c. [28,30]Further the other two peaks in Co 2p spectra adjacent to p 3/2 and p 1/2 , respectively, are correspond to the satellite peaks.The high resolution XPS spectra of C atoms is shown in Figure 4d having three different peaks centered at 281.8, 284.8, and 287 eV that corresponds to CO─Co, C─C, and C─O/C─N bonds, respectively. [31]The highresolution spectra of O1s and N1s is also shown in Figure 4e,f delivering peaks centered at 531.5 and 399.2 eV, respectively, correspond to C─O and C─N bonds.According to the XPS analysis of ZCoPC, the atomic percentage of Co 2p 3/2 and P 2p 3/2 is 2.1% and that of P is 2.2%, respectively, indicating the formation of CoP.

Electrochemical Properties of Electrodes
The electrochemical performance and stability of ZCoPC and its counterparts' electrodes are first evaluated in a three-electrode setup.We have done the electrochemical characterization in KOH electrolyte since oxide and phosphide shows battery type behavior in this electrolyte.However, to optimize the concentration of KOH we have first started with the 6 m KOH electrolyte, however at such high concentration of KOH, the oxygen gas started to evolve at just 0.4 V which can be observed with the rapid current increase in CV (Figure S3, Supporting Information).This limits the positive electrode potential window to just 0.4 V versus Ag/AgCl.Therefore, to increase the positive potential window we reduce the molarity to 1 m KOH in which the satisfactory potential window and coulombic efficiency has been achieved.Further, we performed the CV and GCD analysis for the ZIF-67, ZCoPC-1, and ZCoPC electrode at varying scan rates and current densities as shown in Figure S4 (Supporting Information).The CV of ZIF-67 (Figure S4a, Supporting Information) is showing almost rectangular curve whereas for ZCoPC-1 (Figure S4b, Supporting Information) and ZCoPC (Figure S4c, Supporting Information), the oxidation and reduction peaks are observed very clearly.The peaks can be observed even at 100 mV s −1 of scan rate which shows the fast kinetics of electrolyte ions in the material.This happens because the ZCoPC sample contains different pores, which helps the electrode continue its redox activity even at faster scan rates.Even at higher scan rates, the presence of redox activity confirms that ZCoPC electrodes are capable of producing exceptionally high-rate capability for supercapacitor applications.A suitable ionic conducting path and an electrolyte reservoir are both provided by the hierarchical micro-meso-macro structure of the ZCoPC framework, allowing for the quick ionic mobility of electrolyte ions.These ions are reversibly adsorbed and desorbed and so remains readily available for the redox active sites even at high rate that becomes the basis for charge storage mechanism in this research.GCD analysis as optimized by CV results, are used to evaluate the specific capacity of electrodes.Further, the linear GCD curves is seen for the ZIF-67 (Figure S4d, Supporting Information).The redox behavior of ZCoPC-1 and ZCoPC can also be seen in the GCD curves as shown in Figure S4e,f (Supporting Information), respectively.The chair like non-linear GCD profiles for ZCoPC-1 and ZCoPC can also be observed even at high current densities, indicating the good rate-capability of phosphide electrodes.
The behavior of the CV curve of ZCoPC-1 and ZCoPC is almost same with the presence of prominent redox peaks, but the redox peaks in ZCoPC-1 is less active and have less integrated area under the curve compared to ZCoPC at same scan rate as shown in Figure 5a.The behavior can be attributed to the blocked electrochemical sites in ZCoPC-1 which gets opened after washing with HCl.On the other hand, the CV of ZIF-67 is semi-rectangular correspond to the higher EDLC behavior due to high surface area and less cobalt activity via involvement of binding with organic linker.Further, the insulating framework also restrict the electron transfer which also limit the charge storage capacity.
Further the comparison of GCD for different samples is shown in Figure 5b.The ZCoPC-1 sample is showing lower discharge time with the chair like profile at the same current density indicating the lower redox activity attributed to blocked pores.The same has been deduced from the CV curve analysis.On the other hand, the discharge time of ZIF-67 has been observed to much negligible compared to its counterparts.The low discharge time can be attributed to the high dependence of charge storage contribution from the EDLC behavior rather than EDLC.The redox active material is considered to store same amount of charge in much lower volume compared to EDLC active materials.Further, the absence of electric conductive pathways and majority of microp-ores also limit the charge storage capacity of ZIF-67.The ZCoPC electrode showed the highest specific capacity of 192.6 mAh g −1 as compared to 126.4 and 10 mAh g −1 for ZCoPC-1 and ZIF-67, respectively, using Equation (1). Figure 5c determines the effect of specific capacity w rt current density in which the graphs show inverse characteristic, i.e., the specific capacity falls constantly as the current density rises.
Besides CV and GCD studies, the material was analyzed with impedance spectroscopy and repeated charging-discharging cycles to determine the impedance contribution by the material, as well as its stability as shown in Figure 5d.The Nyquist plot is shown in Figure 5d inset.Two regions (low-frequency region and the high-frequency region) are present in a typical Nyquist plot.The Nyquist plot can be used to determine the charge transfer resistance (R ct ) and the series equivalence resistance (R s ).The length of the semicircle in the high-frequency zone is equal to the R ct , whereas the R s is equal to the length of the abscissa from the origin of the Nyquist plot.In comparison to ZCoPC-1 (2.49Ω cm 2 ) and ZIF-67 (2.68 Ω cm 2 ), the R s for ZCoPC was found to be 2.04 Ω cm 2 , which is the lowest.The great performance of the ZCoPC is due to its low resistance, which is caused by the presence of carbon structures alongside CoP structures as a result of 3D MOF degradation, which produced homogeneously dispersed CoP with carbon.Further, the ZCoPC electrode showed 93.2% of initial capacity retention, whereas the ZCoPC and ZIF-67 showed 90.4% and 81.2% of capacity retention after 5000 charge-discharge cycles.All CV, GCD, and EIS studies showed that the ZCoPC electrode provided improved specific capacity values, impedance, and stability.Further, the CV scan is used to calculate the surface and diffusion charge contribution in the material based on the fact that current from the surface contribution varies directly proportional to the scan rate whereas the current from the diffusion varies with the square root of the scan rate. [32,33]r, Surface controlled current : For, Diffusion controlled current : Surface and diffusion currents are represented by I S and I D , respectively, while k 1 and k 2 are proportionality constants.In the material, both types of processes can be viewed.Hence, the sum of the surface and diffusion-controlled currents equals the total current. Or, Equation ( 7) is the straight-line equation, and the slope and intercept of the straight line may be used to calculate the contribution of the surface and the diffusion-regulated process.The surface and diffusion contribution of ZCoPC, ZCoPC-1, and ZIF-67 is shown in Figure 6a-c, respectively.The highest diffusion has been obtained for the ZCoPC sample due to the fact that high fraction of charge contribution is coming from the redox reactions, however with increased scan rate the fraction of redox reaction decreased and so the surface percentage increased.The increase in surface contribution with scan rate is correspond to the fact that it happens at a faster rate than diffusion.Further, the surface and diffusion contribution for ZCoPC (16.95% and 83.05%, respectively) and ZCoPC-1(16.82% and 83.18%, respectively) at 10 mV s −1 is almost similar to each other which is quite obvious as both samples shared the same redox active material.Although they have different capacity, but the behavior of charge storage characteristics is almost same for both.Apart from this, the charge storage contribution for ZIF-67 is different from the other samples.Due to the much higher surface area, the surface contribution for ZIF-67 (36.07%at 10mV s −1 ) is higher when compared to CoP/Carbon at a same scan rate.

Study of Hybrid Supercapattery Device
A hybrid supercapattery device was also assembled utilizing office paper derived carbon (OPC) based negative electrode and ZCoPC as positive electrode owing to its convincing electrochemical performance.The CV and GCD performance of OPC in 1 m KOH is shown in Figure S5 (Supporting Information).The large CV area of the OPC with quasi-rectangular curve indicate the EDLC type charge storage behavior which is a characteristic of supercapacitors.Further, the linear GCD curves are also supporting the observations.OPC was used as the negative electrode, and it is observed from the CV that it is functional within the range of −0.9-0.0V and degradation of the electrolyte beyond this range.The operational voltage window for the OPC/ZCoPC device is up to 1.4 V as a result of the combined CV of the ZCoPC electrode in the positive and negative window (Figure 7a).
Further, the mass of the electrode has been balanced by keeping the same charge on both the electrodes using Equation (8), where m, C, and V stands for mass, specific capacitance, and potential voltage of the electrode and + and − subscript stands for positive electrode and negative electrode, respectively.The mass balanced electrodes have been used to assemble the device and further tested at different voltage window to practically confirm the working voltage range shown in Figure S6 (Supporting Information).The CV of the assembled supercapattery device was also performed at different scan rates from 5 to 100 mV s −1 and is demonstrated in Figure 7b.At lower scan rates, a deviation from rectangular behavior of the CV profiles is due to the redox active nature of the positive electrode whereas the linear part is the consequence of EDLC behavior of the carbon electrode delivering the hybrid device supercapattery.It's also important to note that as scan rate is increased, the current slowly increases, suggesting that the relationship between scan rate and voltammetry current is linear.This increase in current and EDLC behavior is anticipated given the porous nature of OPC material.The hierarchical pore size of ZCoPC promotes rapid ionic transit and redox activity from meso to macropores which facilitates enhanced performance.Also, at high current densities, a small bend in the discharge curves (as seen in Figure 7c) suggest redox behavior, as well as capacitive nature.However, at low discharge rate a significant bend in the discharge curve can be seen is the consequence of the prominent redox activity for ZCoPC electrode.However, with increasing discharge rate, the disappearance of the non-linear behavior is due to the fact that at high current density, the diffusion controlled redox reactions decreases proportional to square root of the scan rate whereas the surface-controlled decreases proportional to the scan rate.Therefore, redox activity decreases at a much faster rate compared to the surface contribution.Figure 7d shows the trend of specific capacity with current densities.The device shows the highest specific capacity of 116.4 mAh g −1 at 1 A g −1 .The super-capattery device also displayed high-rate performance and so retained ≈65% of the capacity when discharged at 10 A g −1 .Further, the energy and power density are the two most imperative characteristics of energy storage devices.Using Equations ( 2) and (3), the device's energy and power density are computed.The device produced a maximum energy density of 31.6 Wh kg −1 and a corresponding power density of 700 W kg −1 in 1 m KOH electrolyte (Figure 8a).This finding is found to be comparable or even superior to recently published reports in supercapattery field, such as NiCo 2 O 4 /rGO (23.3 Wh kg −1 at 324.9 W kg −1 ), [34] Ni 12 P 5 /PANI (21.9 Wh kg −1 at 373.6 W kg −1 ), [35] ZnP/rGO (24.26 Wh kg −1 at 510 W kg −1 ), [36] PANI/SrTiO 3 (13.2Wh kg −1 at 299 W kg −1 ), [37]  CoMoO 4 (18.89Wh kg −1 at 1.06 kW kg −1 ), [38] NiS 2 /NiV 2 S 4 (19.4Wh kg −1 at 140 W kg −1 ), [39] and Sr 3 P 2 (28.9 Wh kg −1 at 1.02 kW kg −1 ). [40]yquist plot of supercapattery device OPC//ZCoPC is shown in Figure 8b.Almost no semi-circular curve confirms that the device has an extremely low R ct .In addition, based on the actual axis intercept, the device's equivalent series resistance was calculated to be 3.3 Ω cm 2 .In addition, cyclic stability is another crucial criterion to comprehend the viability of the device, along with energy density and power density.The fluctuation of capacity retention with respect to cycle number is seen in Figure 8c.The hybrid device maintained a long cycle life of 92.3% after 10000 cycles.Clearly, the supercapattery device OPC//ZCoPC offers outstanding electrochemical performance based on the high performance positive and negative electrodes.The positive electrode exhibits the excellent battery type behavior with prominent redox peaks like batteries, whereas the negative electrode showed excellent EDLC behavior utilizing the low-cost waste office paper derived activated material.

Conclusion
In this study, MOF has been explored to derive the phosphide carbon composite which shows battery like behavior that can be applied in supercapattery device.The benefit of utilizing MOF to obtain phosphide is the 3D framework of metal and organic linker which delivered the high-quality CoP dispersed with the carbon.Upon thermal degradation, the highly metal dispersed carbon structure can be obtained from the parent MOFs.ZCoPC is used as a working electrode material for energy storage applications due to its synergistic formation of carbon and transition metal phosphide.A three-electrode configuration is used to analyze the diffusion-regulated reaction, which is markedly increased at lower scan speeds.The hybrid supercapattery device additionally exhibits a maximum energy density of 31.6 Wh kg −1 and power density of 700 W kg −1 , with exceptional cyclic stability of 92.3% after 10000 cycles.Our results showed that charge storage technique significantly affects the performance of supercapattery devices.
Advanced Technologies and Materials The Czech Advanced Technology and Research Institute (CATRIN) Palacký University Olomouc Šlechtitelů 27, Olomouc 779 00, Czech Republic P. Dubey Advanced Carbon Products and Metrology Department CSIR-National Physical Laboratory (CSIR-NPL) New Delhi 110012, India Mansi CSIR-Central Scientific Instruments Organization Sector 30-C, Chandigarh 160030, India A. Deep Institute of Nano Science and Technology (INST) Sector-81, Mohali, Punjab 140306, India

Figure 1 .
Figure 1.Schematic showing the brief methodology of the ZIF-67 derived ZCoPC and OPC based hybrid supercapattery.

Figure 2 .
Figure 2. Material Characterization of ZCoPC and ZCoPC-1 sample a) XRD and b) Raman spectra c) N 2 adsorption-desorption isotherm, and d) pore size distribution curve.

Figure 7 .
Figure 7. a) Combined voltage window of ZCoPC as positive and OPC as negative electrode, b) CV, c) GCD, and d) rate performance of the OPC//ZCoPC.