With advancements in industry and commercial sector, there are many factors which create hindrance in their fast growth in which energy shortage is a serious problem. There are many sources for energy production and used different pollution causing fuels like fossil fuels, biomass, and furnace oil. These energy resources produce electricity but mostly energy is not stored properly due to wastage of these fuels. This energy storage is very useful for small electronic instruments and electric vehicles (EV), Li-ion batteries (LIBs) [1,2]. LIBs have many limitations, i.e., risk for environment due to explosive nature of lithium and hazardous effects of fossil fuels. Among energy storage devices, supercapacitors performed better than classical LIBs and simple capacitors because of good combination of energy and power densities along with good capacity retention especially in case of asymmetric super capacitors (ASC). They are the combination of both pseudo capacitors (PD) (battery like properties) and electric double layer capacitors (EDLC) (capacitor like properties) [3–5].

Supercapacitors used expensive noble metals active materials like ruthenium oxide (RuO₂), iridium oxide (IrO₂), lithium cobalt oxide (LiCoO₂), lithium Iron phosphate (LiFePO₄) and platinum/carbon (Pt/C) which limit their commercial use on the large scale [6–12]. There are different factors like size, porosity and conductivity which control the electrochemical performance [13,14]. The low cost, abundant nature of hierarchical nanomaterials with good surface area are more appealing for energy storage applications. The structures which have many pores have good faradic reaction due to the reason that they have which more active electrochemical reaction sites [15,16]. Nanoporous solids having porosity dimensions from meso- (2–50 nm), micro- (<2 nm), to macropores (>50 nm), can lodge and serve as host for metallic atoms, ions for ideal faradic reaction [17–19]. Particularly the mesoporous materials can serve as ideal electrochemically active materials due to tunable porosity, large void space, and highly exposed surface area. Due to these excellent properties, mesoporous materials can efficiently be used in many novel applications like biotechnology, sensors, adsorption/separation, energy storage and conversion [20–27]. The two most thoroughly researched mesoporous compositions since 1990s are organosilicas and periodic mesoporous silicas, i.e., sulfides and oxides (PMSs and PMOs) [28–31]. However, apart from the expensive and short range of organosilane coupling molecules, their use in energy storage and conversion applications can be hindered owing to their insulating nature. For this, the non-siliceous mesoporous materials proved to be more commendable materials due to assorted chemistry and functionality [32–34]. Metal phosphates, phosphides, and phosphonates are good potential non-siliceous mesoporous materials due to good structural and electrochemical properties. Metal phosphates seeks significant attention to be used as active catalysts due to good acidic and redox behavior at high rates [35–37].

Different transition metal phosphates (TMPs) (Ni, Mn, V, Zr, etc.) have intriguing properties like layered structures with open framework let the proton of acidic group to diffuse through the inter spacing between the layers which make them good conductor for protonic exchange and intercalation of metallic ions [38–40]. Additionally, variable valences of metallic ions could increase the faradic redox reaction. Metal phosphonates have metals linked with phosphonic binders at molecular level [41–43]. Phosphonic acids and the linked compounds have more potential to be bond with different metallic ions. Organic and inorganic molecules linkages results in formation of P–O–M (M = metal) bonds which leads to excellent stable chemical and thermal structures [44–46]. The diverse phosphorus group facilitates its functionalization with different types of functional groups. Their practical use can be enhanced due to modulation of phosphonic group with different functional groups with tailored desirable properties [47–51]. There are other phosphonic group materials like metal phosphides formed by metallic bonds of phosphorus and metallic elements. The novel features of metal phosphides are metalloid and ceramic properties which endorsed effective thermal and chemical stability, good mechanical strength, excellent heat and electric conductivity [52–57]. These all stated factors make transition metal phosphates more distinctive as compared to metal oxides [58,59]. Additionally, they have other features like good catalytic properties in water splitting and ever-lasting stability [60–62]. These important properties make them most favorable for electrochemical capacitors and batteries. Different heteroatoms TMPs reported in literature like ammonium metal phosphates (AMPs), NH₄MPO₄·H₂O (M = Co²⁺, Ni²⁺, Fe²⁺, and Mn²⁺) [63–68], Mn₃(PO₄)₂, Ni₃(PO₄)₂, VOPO₄, etc. [69,70] can be used for energy conversion and storage applications. The reasons for these properties are good electrochemical properties, effective electrical stability and nanostructures favorable for ionic mobility in different sodium/lithium metal phosphates (NaFe-PO₄, LiMnPO₄, LiFePO₄, and LiNiPO₄) for batteries [71–74]. AMPs have highly conductive sheets which are produced by slanted corners of MO₆ with good interconnected NH₄⁺ and PO₄³⁻ ions through hydrogen bonding. This will results in good faradic reaction in between inorganic sheets and efficient metallic ions intercalations with a lot of electrochemical reaction sites [70]. TMPs have excellent electrochemical properties in term of energy efficiency, environmental friendliness, structural integrity and safety evaluation as compared to transition metal oxides (TMOs) and hydroxides (TMHs) [15,17,18]. Like equally arranged olivine structure with general formula LiMPO₄ (M = Fe, Co, Mn, or Ni) has been used on large scale as cathode materials in batteries. Oxygen octahedral sites engaged by other metal ions produced due to durable and strong covalent bonding in tetrahedral anions (XO₄)_n [20]. Lithium–manganese and lithium–iron-based phosphates have been identified as potential positive ions in the olivine structure among the various metal atom replacements. This is primarily because it is inexpensive, environmentally inert, stable while cycle, and highly reversible.

Contrary to many important merits, TMPs have many different drawbacks like low structural integrity, less durability which induced many unfortunate features like phase transformation, limited cyclic life, less structural stability, and electrical conductivity [55,75,76]. These unfavorable factors completely influence electrochemical properties of all composites and can be fixed by inducing mesoporosity, effective rate capability, effective electrical and thermal conductivity, greatly exposed surface area and impressive cyclic behavior [13]. These factors along with mechanical and thermal properties can be endorsed by incorporating carbonaceous materials like reduced graphene oxides (rGO), multi-walled carbon nanotubes (MWCNTs) and graphitic carbons (GC) [77–81]. Additionally, specific capacity, energy of TMPs and carbonaceous materials are not too high due to their capacitive behavior which can be catered by functionalization of MWCNTs, rGO, and GC with conducting polymers like polyaniline (PANI) (highest theoretical capacitance of 3407 F g⁻¹), polystyrene (PS), polypropylene (PPY), and other conducting polymers [82,83]. This can be achieved by formation of more stable and durable functionalization with conducting polymers along with reversible pseudocapacitive behavior and impressive rate capability [82,84]. Although there are few reviews on different TMPs, but to the authors knowledge there has been no review on TMPs/carbon-based materials which will be very helpful for opening the era for practical research with excellent combination of electrochemical properties. This review article extensively reviews the maximum available studies discussed in literature related to unary, binary, and ternary TMPs and their composites with MWCNTs, reduced graphene oxide (rGO) and other carbon-based materials.

UMPs are the single transition metal (Ni, Co, Zn, V) phosphates. Metal phosphates have low conductivity, surface area, porosity which results in their low electrochemical properties. But when their hybrids with carbonaceous materials (CNTs and GRA) then their surface area, conductivity, porosity increased which results in increased electrochemical performance. Following is the comparison electrochemical performance of pristine UMPs and their hybrids.

BMPs are the Double transition metal (Ni, Co, Zn, V) phosphates. Double transition metal has good electrochemical properties as compared to UMPs due to more ions available for their diffusion and effective faradic response. But still these metal phosphates have low conductivity, surface area, porosity which results in their low electrochemical properties. But when their hybrids with carbonaceous materials (CNTs, GRA) then their surface area, conductivity, porosity increased which results in increased electrochemical performance. Following is the comparison electrochemical performance of pristine BMPs and their hybrids.

TMPs are the triple transition metal (Ni, Co, Zn, V) phosphates. Triple transition metal has good electrochemical properties as compared to BMPs and UMPs due to more ions of three metals available for their diffusion and effective faradic response. But still these metal phosphates have low conductivity, surface area, porosity which results in their low electrochemical properties. But when their hybrids with carbonaceous materials (PANI/CNTs) then their surface area, conductivity, porosity increased which results in increased electrochemical performance. Following is the comparison electrochemical performance of pristine TMPs and their hybrids.

A few important factors like surface area, conductivity, pore size are certain physiochemical properties affect the electrochemical performance of supercapacitors. Here in this section, it has been tried to discuss the effect of electrochemical performance of different unary, binary, and ternary metal phosphates with the combination of carbon-based materials. This performance is due to hierarchical structures which engrossed good porosity and increased surface area with the inclusion of carbon-based materials. Table 5 discussed the some studies like nanosheets of MnPO₄·H₂O/MWCNT have high surface area of 19.6 m² g⁻¹ and 20 nm pore size as compared to pristine MnPO₄·H₂O (11.8 m² g⁻¹) with pore size of 17.7 nm [96]. NiP50CNT50 has highest surface area (32.2 m² g⁻¹) [95] as compared to pristine Ni₃(PO₄)₂ (16.98 m² g⁻¹) [147]. Nickel phosphates on rGO sheets mesoporous hierarchical structure of Ni₃(PO₄)₂/rGO-300 has greater surface area (198.72 m² g⁻¹) [148] than pristine Ni₃(PO₄)₂ (16.98 m² g⁻¹) nanosheets [147]. NMP balls wrapped on MWCNTs nanosheets has high surface area of 285.4 m² g⁻¹ than pristine NMP (209.2 m² g⁻¹) and low pore size with pore size of 13.2 nm then pristine (18 nm) [128]. Flower like micro cuboid mesoporous structure of CNPMM_1:1 has greater surface area of 11.7 m² g⁻¹ then flower like micro hexagonal structure pristine CNP (5.3 m² g⁻¹) and high porosity (29.4 nm) as compared to pristine CNP (8.7 nm) [131]. These different mesoporous morphologies like nanosheets, nanorods, and flower like microsphere have increased porosity, surface area, conductivity. These porous sites act as electrochemical reaction sites which increase the ionic diffusion resulted in increased oxidation and reduction reactions results in increment of electrochemical performance. Due to all these reasons hybrid metal phosphates/carbonaceous materials have good electrochemical properties in comparison to their relative pristine.

Current section is presented a comprehensive discussion about the reported studies on different unary, binary and ternary metal phospahtes with CNTs and graphene based materials. This discussion is the comprehensive comparison of hybrid composite of TMPs and carbon based materials with their pristine materials. Fig. 6 represents all objectives which have been attained in this review article. Fig. 7,–9 represents specific capacity, energy and power desities and cyclic performances comparison of all hybrid composite electrodes and their representative SSC and ASC devices with their respective pristine materials. Sharmila et al. [96] synthesized MnPO₄·H₂O/MWCNT nanocomposite. The reported specific capacity was 765 F g⁻¹ pretty much greater then pristine MnPO₄·H₂O (145 F g⁻¹) [149]. The electrochemical performance of SSC was 15 Wh kg⁻¹ and 350 W kg⁻¹ with capacitance retention of 94% after 5000 cycles greater then pristine MnPO₄//AC (14.89 Wh kg⁻¹ and 1400 W kg⁻¹; 88.9% after 5000 cycles) [150]. The good electrochemical results were due to highly conductive MWCNT. The batter SSC performance was attributed to combined EDLC and pseudo capacitive nature of MWCNTs and MnPO₄·H₂O NSs respectively due to less ionic decomposition and enhanced ionic transfer [96]. Dutta et al. [94] prepared VOPO₄·2H₂O/MWCNT through the method explained in previously reported literature. The specific capacitance reported was 236 F g⁻¹ at 5 mVs⁻¹ scan rate pretty much higher than pristine VOPO₄ (202 F g⁻¹ at 2 mV s⁻¹) [151]. The reported energy and power densities of nanocomposite were 65.6 Wh kg⁻¹ and 1476 W kg⁻¹ greater the pristine VOPO₄·2H₂O supercapacitor (18.7Wh kg⁻¹ @290 W kg⁻¹) [151]. The reason for best performance was uniform mixing of VOPO₄ and MWCNT which formed the hierarchical mesoporous structure ideal for ionic and electronic intercalation [93]. Tian et al. [99] prepared Ni₂P @CNT nanocomposites through microwave irradiation method. The capacitance of 854 F g⁻¹ at 1 A g⁻¹ more as compared to pristine Ni₂P (418 F g⁻¹ @1 A g⁻¹) [107]. The ASC device of Ni₂P @CNT//AC were 33.5 Wh kg⁻¹ energy density and 387.5 W kg⁻¹ power density with capacitance retention of 84% after 5000 cycles pretty much greater then pristine Ni₂P₂O₇·8H₂O//rGO (26.6Wh kg⁻¹ @870.6W kg⁻¹; 87.35% after 5500 cycles) [152]. The superior electrochemical performance was due to porosity engrossed which have good electrochemical reaction sites [99,102]. The other reasons were high surface area and uniform growth of Ni₂P over CNTs which is ideal for all electrochemical performance [99,103–106]. Shehzad et al. [95] prepared NiP-CNT nanocomposite via sonochemical synthesis. NiP50CNT50 showed capacity of 845 C g⁻¹ at 0.6 A g⁻¹ pretty much more as compared to pristine NiP (600.6 C g⁻¹ at 0.6 A g⁻¹). The ASC device of NiP50CNT50 showed energy and power densities of 94.5 Wh kg⁻¹ and 340 W kg⁻¹ with capacity retention of 95.5% after 5000 cycles greater then pristine Ni₃(PO₄)₂//AC (26.8 Wh kg⁻¹ @750 W kg⁻¹; 87% after 5000 cycles) [153]. The reason for superb electrochemical performance was high conductivity and exposed surface area of 32.4 m² g⁻¹ owing to combined effect of both NiP and CNTs, adsorbed gas volume (168 cm³ g⁻¹), and mesoporosity as indicated by hysteresis in BET analysis. These pores act as the active electrochemical reaction sites. The high cyclic performance was due to homogeneous dispersion of MWCNTs. Mirghni et al. [76] synthesized Ni₃(PO₄)₂/GF through hydrothermal process. Ni₃(PO₄)₂/90 mg GF showed more electrochemical performance of 48 mAh g⁻¹ at 0.5 A g⁻¹ greater than pristine Ni₃(PO₄)₂. The electrochemical performance of ASC device of Ni₃(PO₄)₂/90 mg GF//C-FP was 49 Wh kg⁻¹ @499 W kg⁻¹ and cyclic performance of 92% after 2000 cycles pretty much greater than pristine Ni₃(PO₄)₂//AC (26.8 Wh kg⁻¹ at 750 W kg⁻¹; 87% after 5000 cycles) [153]. The best performance was due to GF nano-rods networks having many pores which were ideal for faradic reaction to takes place. Iqbal et al. [108] synthesized ZnP with the help of sonochemical method followed physical blending to form ZnP_rGO composite. ZnP_rGO_30% showed 278 F g⁻¹ due to uniform distribution much higher than pristine ZnP (59.81 F g⁻¹). The reported causes for the good performance of was due to high porosity and surface area which facilitates faradic reaction for efficient flow of OH-ions, all will lead to effective faradic reaction.

Mirghni et al. [109] prepared Mn₃(PO₄)₂/GF composite through hydrothermal route. The more specific capacitance of Mn₃(PO₄)₂/100 mg GF (270 F g⁻¹ @0.5 A g⁻¹) as compared to pristine Mn₃(PO₄)₂ (213 F g⁻¹ at 5 mV s⁻¹) [154]. The ASC device of Mn₃(PO₄)₂/100 mg GF//AC showed 7.6 Wh kg⁻¹ and 360 W kg⁻¹ with cyclic performance of 96% after 10000 cycles pretty much greater than pristine Mn PO₄//GO (2.271 Wh kg⁻¹@1.5×10⁵ W kg⁻¹; 85.3% after 1000 cycles) [155]. The best performance was attributed to strong bonding of uniformly deposited GF sheets on Mn₃(PO₄)₂ micro rods with excellent electrical conductivity. This resulted in increment of specific capacity due to stable conductive paths which facilitate the good metallic ions conduction with electrolyte [109]. Mahmoud et al. [111] synthesized Co₃(PO₄)₂/GF by dispersion of GF in DI water via ultra-sonication approach with specific capacitance of 57 mAh g⁻¹ much greater then pristine Co₃(PO₄)₂. The ASC device of Co₃(PO₄)₂/20 mg GF//ppAC ASC device showed 24 Wh kg⁻¹ and 468 W kg⁻¹ respectively with cyclic performance of 80% after 10000 cycles batter then pristine Co₃(PO₄)₂ (80% after 6000 cycles) and Co₃P₂O₈·8H₂O//AC (11.9 Wh kg⁻¹ @3590 W kg⁻¹) [110]. The good performance was due to GF which enhanced electrical conductivity and results in formation of conductive and leads to effective faradic reaction.

Dang et al. [118] prepared P-CSs @Ni₁-Co₂-P NSs through hydrothermal carbonization method. The specific capacitance of nanocomposites was 1040.3 F g⁻¹ at 1 A g⁻¹ [117] greater than pristine NCCF-3 (811.1 F g⁻¹ of 1.25 Ag⁻¹) [156]. At high current density of 30 A g⁻¹, it retained to 505.5 F g⁻¹. The ASC device of P-CSs@Ni₁-Co₂-P NSs//AC showed 16.5 Wh kg⁻¹ energy density @power density of 750 W kg⁻¹. The 3D interlocked uniformly gowned Ni₁-Co₂-P NSs on carbon spheres form a network which controlled with the help of low hydrothermal temperature (160°C) [117]. The causes for batter performance of composite. The reasons for batter electrochemical performance of nanocomposite were presence of many mesopores results in effective transport paths for ideal electronic and ionic conduction. This is all due to transformation of Ni₁-Co₂-P NSs @CSs into P-CSs @Ni₁-Co₂-P NSs through phosphorization. Kim et al. [85] synthesized VPO/CNFs nanostructures with the help of carbonaceous materials like CNTs. The maximum specific capacitance of CNTs @VPO @CNFs composite reported was 576.1 F g⁻¹ at 0.66 A g⁻¹ more as compared to pristine VOPO₄ (~247 F g⁻¹ @0.5 A g⁻¹). The SSCD device of CNTs @VPO @CNFs showed energy density of 69.1 Wh kg⁻¹ and 3200 W kg⁻¹ with cyclic performance of 109% after 10000 cycles pretty much greater than pristine VOPO₄·2H₂O (18.7 Wh kg⁻¹ at 290 W kg⁻¹) [151]. The best electrochemical properties were attributed to increased conductivity of CNTs forest and VPO @CNFs. Sharmila et al. [128] prepared MWCNTs wrapped NMP via mortar/pistol method. The specific capacity of hybrid composite was 812 F g⁻¹ @2 A g⁻¹ greater than pristine NMP (24 F g⁻¹) due to inclusion of mesoporous MWCNTs rods. The ASC device of NMP:MWCNTs//AC presents 78 Wh kg⁻¹ and 698 W kg⁻¹ with cyclic stability of 90% after 5000 GCD cycles respectively greater then pristine cobalt manganese phosphate//reduced graphene oxide ASC (84% after 6000 cycles) [157] and NiMn(PO₄)₂//AC (64.2 Wh kg⁻¹ @340 W kg⁻¹) [158]. The other reason for better electrochemical performance was highly exposed surface area due to nano-rods with many several pores which act as electrochemically active reaction sites [128]. Yang et al. [136] prepared N-CNTs @NiCoP/CoP through hydrothermal method. The specific capacitance of nanocomposite was 152 mAh g⁻¹ @1 A g⁻¹ greater than pristine NiCoP/CoP (112 mAh g⁻¹). This all was due to thorough interlocked linking of N-CNTs with NiCoP/CoP which results in uniform core-shelled mesh structure with highly exposed surface area and causes more effective ionic and electronic intercalation.

Zhang et al. [137] synthesized Ni-Co-P/PO_x/C through hydrothermal approach. The specific capacity reported was 583 C g⁻¹ at 1 A g⁻¹ greater then pristine Ni-Co-P (453 C g⁻¹ at 1 A g⁻¹) [145]. The ASC device of Ni-Co-P/PO_x/C//rGO/NF presented electrochemical performance of 35.79 Wh kg⁻¹ @800 W kg⁻¹ with capacitance retention of 83.6% after 5000 cycles more than pristine NaNi_0.33Co_0.67PO₄·H₂O//Gra (29.85Wh kg⁻¹ @374.95Wkg⁻¹; 76.9% after 10000 cycles) [159]. The effective electrical properties were due to nanopores in phosphate and phosphide phase because of its amorphous nature and highly conductive carbon nanosheets. Wang et al. [131] CNPMM_1:1 fabricated via hydrothermal approach. The specific capacity of CNPMM_1:1 was 2334 mAh g⁻¹ greater than pristine CNP (2131 mAh g⁻¹). The reported reason for this performance was that at high current density –OH ions have insufficient time for diffusion in electrode surface and at low current density, they have sufficient time for diffusion. This resulted in large charge storage at low current density makes it potential candidate to be used in high power applications [133]. The other reason for best electrochemical performance CNPMM_1:1 was the added effect of MnO₂, CNP, and MWCNTs in phosphates matrix.

Fan et al. [140] prepared NiCo (PO₄)₃/GF composite through hydrothermal approach. The reported specific capacity of composite was 86.4 mAh g⁻¹ greater than pure nickel cobalt phosphate (64 mAh g⁻¹). Electrochemical performance of ASC device to be 34.8 Wh kg⁻¹ @377 W kg⁻¹ with cyclic performance of 95% after 10000 cycles moe than pristine NaNi_0.33Co_0.67PO₄·H₂O//Gra (29.85 Wh kg⁻¹ @374.95 W kg⁻¹; 76.9% after 10000 cycles) [159]. The batter electrical properties were due to synergic effects of conductive with highly exposed surface area GF and NiCo(PO₄)₃. Mirghni et al. [142] synthesized NiMn(PO₄)₂/GF composite by hydrothermal process. The specific capacity of NiMn(PO₄)₂/GF reported was 97 mAh g⁻¹ at 0.5 A g⁻¹ pretty much higher than NiMn (PO₄)₂ (63 mAh g⁻¹) [141]. NiMn(PO₄)₂/GF//ppAC ASC device presented energy and power density of 35.42 Wh kg⁻¹ and 538 W kg⁻¹ respectively with capacitance retention of 97.8% after 10000 cycles greater than Mn₃(PO₄)₂//AC (11.7 Wh kg⁻¹ @1410 W kg⁻¹; 99% after 9000 cycles) [149]. The good electrochemical performance was due to combined synergic effect of highly electroactive pseudocapacitive Mn and Ni [142]. Other reason was the interaction between GF and NiMn (PO₄)₂ which results in more effective ionic conduction [141]. Raja et al. [160] synthesized ZAPG2 with specific capacity of 416 F g⁻¹ @1 A g⁻¹ pretty much greater then pristine pretty much greater then pristine ZAP (328 F g⁻¹ @1 A g⁻¹).

Transition metal phosphates (TMPs) have very impressive properties like layered structures with open framework which make them good capable for protonic exchange and ionic intercalation in between different layers. Additionally, variable valencies of metallic ions enhanced the faradic redox reaction. TMPs have good energy efficiency, environmental friendliness, structural integrity, and safety evaluation compared to TMOs and TMHs. Despite some advantages, there are many disadvantages of TMPs like less structural stability, poor capacitance retention, less structural integrity, and electrical conductivity. These demerits can be catered by using TMPs with carbonaceous materials like reduced graphene oxides (rGO), multi-walled carbon nanotubes (MWCNTs), and graphitic carbons (GC). These hybrid materials have mesoporosity, good exposed surface area, layered structure, good conducting paths and excellent cyclic performance. This review comprehensive summarizes all possible reported studies of unary, binary TMPs with carbon-based materials and discuss their electrochemical performance in comparison with the pristine TMPs. These materials have been used in many practical applications like electrical vehicles, electronics appliances etc.

Although this review comprehensively discusses hybrid unary, binary, and ternary metal phosphates with carbon-based materials. But in literature there has been no study reported on ternary and quaternary metal phosphates/carbon-based materials. These materials are very important and need to be studied because they will display more effective ionic and electronic intercalation which results in redox rich faradic reaction so good electrochemical performance. Furthermore, the more stable chemical grafting of metal phosphates and carbon – based materials are more useful as compared to physical coupling of precursors. As stable chemical grafting led to batter rate performance and good capacitance retention as compared to physical due to formation of stable functional groups. Second, if we talk about preparation methods, mostly hydrothermal, solvothermal, co-precipitation, sintering, chemical deposition methods and some other methods have been discussed. Bus only one material (NiP50CNT50) prepared by sonochemical approach. This preparation process opens a new gateway in preparing nanocomposites with superb electrochemical performance. The reasons are due to molecular level grafting aided with acoustic cavitation effect. This uniformly formed nanoscale layered structure on molecular level results in very rich faradic reaction due to highest exposed surface area, conduction layered structure which makes these materials potential as positive electrode materials in energy storge devices (supercapacitors) applications.