Conventional Dye-sensitized Solar Cells Research Articles

Bay-substituted Perylene diimides (PDIs) as redox mediators in dye-sensitized solar cells and active electrode material in supercapacitors

In recent years, innovations in materials design have improved the optoelectronic properties of advanced materials and facilitated their efficient utilization. A significant amount of research has been conducted on developing perylene diimide (PDI) dyes for their use in various energy-related applications. In the present work, we have synthesized bay-substituted PDI derivatives and explored their dual applications in energy harvesting and storage devices. The nucleophilic substitution reaction of 1,7/1,6-brominated Val-PDI was performed by using 2-naphthol (N) and its Nitrogen analogue 8-hydroxy quinoline (Q) for analysing the effect of N-heterocycle at the bay position. The prepared 1,7 (N1/Q1) and 1,6 (N2/Q2) PDIs underwent thorough photophysical and electrochemical analyses and their structures were optimized through density functional theory (DFT) using B3LYP approach with a 6-31+G (d,p) basis set. Although all the prepared bay-substituted PDIs showed reasonable redox activity, N1 was chosen as an electrolyte dopant in dye-sensitized solar cells (DSSC) owing to its band alignment. This aided in enhanced electron lifetime and charge transfer properties, which led to an enhanced efficiency of 2.04 % while the conventional DSSC delivered only 1.84 % at 200 W m−2 illumination. Additionally, the symmetrical supercapacitor fabricated by using Q1 as electrode material generated a high specific capacitance of 146.54 F g−1. Thus, the proposed work opens avenues for the utility of bay-substituted PDI derivatives for organic electronic applications.

Natural dyes (Tithonia diversifolia, Tagetes minuta and Bidens pilosa) sensitized solar cells with reduced graphene based electrodes

The search for suitable alternatives to non-renewable polluting energy sources is a continuous and an active undertaking. There is particular focus towards production of low cost, eco-friendly and more efficient dye sensitized solar cells (DSSCs). Natural dyes DSSCs have the capability of generating green energy at low production cost and hence become a promising class of photovoltaic cells. However, there are inherent problems encountered by the conventional DSSCs including photoanode and cathode related problems such as high cost and electron-hole recombination resulting in a low rate of photoelectric conversion efficiency. In this work, organic dyes from Tithonia diversifolia, Tagetes minuta and Bidens pilosa were used as sensitizers as replacement of synthetic dyes of the conventional DSSCs. The study in addition sought to replace conventional photoanode and cathodes with rGO-TiO2 photo anode and rGO counter electrode. The Tithonia diversifolia has one absorption peak at 665 nm indicating the presence of chlorophyll dye while Tagetes minuta has absorbption peaks at 534 nm suggestive of anthocyanin dye (a flavonoid), 607 nm and 660 nm confirming the presence of chlorophyll a dyes while Bidens pilosa has an absorption peak at 665 nm which again suggests the presence of chlorophyll dye. The tendency of the three natural dyes to absorb in the regions above 650 nm indicates their usefulness for use as dyes for DSSC. The I-V curves of the fabricated natural DSSCs show that when TiO2 is used as the photo anode, Tithonia diversifolia registered a higher efficiency of 0.18 % while Tagetes minuta had the lowest efficiency of 0.08 %. When rGO is incorporated in the TiO2 photo anode, there is an improvement in the solar cell efficiency for all the fabricated DSSCs with Tithonia diversifolia having the highest at 1.56 %. Thus incorporating rGO in the TiO2 photo anode greatly improved the power conversion efficiency of the DSSC. Tithonia diversifolia dye had the highest efficiency which may be attributed to the concentration of the chlorophyll dye.

Stability Modification of Dye-sensitized Solar Cells by Ruthenium Dyes Embedded on Eggshell Membranes.

Dye-sensitized solar cells (DSSCs) have been one of the most promising technologies to convert sunlight into electricity repeatedly based on the mechanism that dyes inject/accept electron into the metal oxides/from redox mediator. Specifically, N719 ([RuL2(NCS)2], L: 4,4'-dicarboxy-2,2'-bipyridine), immobilized on TiO2 through the interaction between its ligands (-COO- and -NCS) and the oxygen on the TiO2 surface, has been used as a conventional DSSC dye with high voltage. Nevertheless, -NCS ligands have been removed from Ru2+ in N719 due to UV irradiation and exchanged with H2O or OH- in electrolyte, resulting in voltage drop. In this work, we developed the first DSSC using the N719-adsorbed Eggshell (ESM)-TiO2 composite to maintain the immobilization of N719 on TiO2 through electrostatic interaction between the protein of ESM and N719. The DSSC using the composite maintained the voltage even after 12 h light irradiation, although the voltage of DSSC without ESM dropped drastically. It means that the ESM contributed to stable photovoltaic performances of DSSCs through the protection of NCS ligands of N719.

Fabrication of transparent TiO2-GO nanocomposites deposited on vertically aligned ZnO nanowire arrays as hybrid nanostructured photo-anode for dye-sensitized solar cells

In this article, we report the fabrication of hybrid nanostructures comprised of vertically aligned Zinc Oxide (ZnO) nanowires (NWs) coated with titanium dioxide-graphene oxide (TiO2-GO) nanocomposites by easy, cost-effective, chemical method and demonstrate their utilization as photo-anode for dye-sensitized solar cells (DSSCs). A thin layer of transparent TiO2 with varying GO amount is deposited on top of vertical ZnO NW arrays by sol-gel spin coating method. A conventional DSSC structure is fabricated by using hybrid structure as photo-anode, ruthenium based N3 dye as photosensitizers, iodine solution (I−/I3+) as electrolyte and fluorine-doped tin oxide (FTO) coated glass substrate as counter electrode. The fabricated hybrid nanostructure based DSSC exhibits enhanced power conversion efficiency (η) compared to that of pristine ZnO NW photo-anode. Also, other characteristic parameters of DSSCs like open-circuit voltage (Voc), short-circuit current density (Jsc) and fill factor (FF) are estimated from the current density-voltage (J-V) relation measured under illumination of 1 sun (100 mW/cm2) solar spectrum for ZnO NW/TiO2-GO hybrid nanostructures. Improvement in these obtained parameters is observed with increasing GO amount in the TiO2-GO nanocomposite layers deposited on top of ZnO NW arrays. Best performance is delivered by the hybrid nanostructure consists of ZnO NW/TiO2-GO (10%)with optimized value of η ∼0.72% along with Voc ∼491 mV, Jsc ∼2.19 mA/cm2 and FF ∼0.66. This betterment in performance is attributed to the combined effects of improvement in charge transport through the axis of ZnO NWs, increment in contact area and modulation of conductivity of TiO2 by inclusion of conducting GO network. The modulation in charge transport properties of hybrid nanostructures with varying GO amount is studied by complex impedance spectroscopic analyses. The study indicates that particular amount of GO significantly modifies the interfacial effects in fabricated hybrid nanostructures to facilitate better charge transportation.

Role of Pi-Electron Density at the Interface of Small Molecule-Sensitized Solar Cells

Conventional dye-sensitized solar cells (DSSCs) involving charge-transfer interfaces face charge injection losses and offsets for TiO2-sensitizer band alignment. The direct charge-transfer mechanism in DSSCs with catechol (CT, 1,2-benzenediol)-based compounds minimizes the injection losses and eliminates band alignment issues, although the photovoltaic performance of the corresponding device is very poor due to the ultrafast (picosecond) recombination of photoexcited electrons. Just as in a natural photosystem, structural selectivity toward inhibition of this recombination needs to be defined. The interfacial electron density and back electron transfer kinetics at the molecular sensitizer–TiO2 interface play a significant role in the overall energy conversion efficiency. Herein, we identified, for the first time, that the π-electron cloud at the sensitizer–TiO2 interface facilitates the degree of recombination. Comparative density functional theory analyses confirmed that these electron clouds act as large recombination sites. Luminol (LM) and isoluminol (ILM) were employed as “small molecule” sensitizers without the cloud, having a secondary amine linker, which increased the photoenergy conversion efficiency of the single-step sensitization-based photovoltaic cell (type-II DSSC) by reducing the recombination. The device with LM exhibited a power-conversion efficiency (PCE) of ca. 1.11% (representing 363% improvement when compared to CT), the highest ever reported in this category. This understanding is insightful for the design of novel small molecular sensitizers for future DSSCs.

Cylindrical transparent conductive oxide-free dye-sensitized solar cells with treated flat titanium sheet

Conventional dye-sensitized solar cells (DSSCs) require two transparent conductive oxide (TCO) glasses as working and counter electrodes and are one of the most costly components posing an appreciable cost burden for production and commercialization. To circumvent this issue, we propose a TCO-free device structure utilizing titanium (Ti) sheets as a substitute for TCO. This back contact device structure not only allows the removal of the costly TCO component from the working electrode but also enhances the extent of photons absorbed by the photoanode. A flat titanium sheet with microholes (FTS-MH) was successfully applied to fabricate cylindrical TCO-free-DSSCs) with a titanium sheet as a back contact electrode. When the H2O2 surface-treated FTS-MH substrate generating dense anatase TiO2 nanosheets was used as a photoanode, there was a pronounced improvement in efficiency from 5.76% to 8.59%. This was mainly attributed to the lower interfacial resistance facilitated by improved electrical contact between the conducting FTS-MH substrate and mesoporous TiO2 layer since enhancement in the dye loading was only 8.6%.

Near-infrared light harvesting of upconverting Y2O3:Er3+ nanoparticles and their photovoltaic application

Light harvesting plays a significant role in the enhancement on photovoltaic performance. It is closely associated with the photocurrent of solar cells. It is possible to improve light harvesting by material substitution as well as expansion of absorptive edge. Therefore, upconversion characteristics is one of promising solutions for better light harvesting. Upconverting materials emit visible light which is available for photoconversion after they absorb invisible near-infrared (NIR) light. In this study, Er3+ doped Y2O3 (Y2O3:Er3+) nanoparticles were used as upconverting material. Its strong emissions of green and red light corresponding to 2H11/2 and 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions were clearly demonstrated under NIR irradiation of 975 nm wavelength. These emissions were apparently absorbed by dye-sensitized electrode. Based on these results, Y2O3:Er3+ nanoparticles were introduced into dye-sensitized solar cells (DSCs). After incorporating Y2O3:Er3+ nanoparticles, photovoltage was increased due to its high band-gap energy of about 5 eV. On the other hand, the photocurrent was decreased because of the decrease in adsorbed dye amount and electron paths. However, the photoconversion edge was obviously expanded. As a result, DSC performance was enhanced with optimum upconverting particles. It exhibited an efficiency of 8.03%, which was higher than that of a conventional DSC.

High-Efficiency Dye-Sensitized Solar Cells: A Comprehensive Review

Keeping in mind our community's dependency on non-renewable sources of energy, it is a gravitating issue that seeks our attention and requires us to switch to renewable sources of energy at the earliest. A Dye-Sensitized Solar Cell (DSSC) is a third-generation photovoltaic technology that has immense capability to become highly commercial in a few years. Along the same lines, it is necessary to highlight that current DSSCs have shallow lifetime values, stability and performance. The efficiency of current DSSCs and the need to tackle their choice of materials and long-term stability is a concern. Some of the highest recorded efficiency values are around 12%, and this calls for severe replacement of conventional DSSC materials, modifications in the device structure and molecules, and improvement in testing and scaling-up measures. This review article underlines an introduction to DSSCs, working principle, components, high-efficiency DSSCs, strategies to improve device performance, DSSCs research in India, the advantages and disadvantages of the device, and recent research on fruit and flower-based DSSCs. Keywords: Dye-Sensitized Solar Cells, Solar Cell Materials, Third Generation Photovoltaics, High-Efficiency Dye-Sensitized Solar Cells, Solar Cells.

PEDOT-graphene counter-electrode for solar and improved artificial light conversion in regular, bifacial and FTO-less cobalt mediated DSSCs

Dye-sensitized solar cells (DSSC) are emerging as an attractive indoor photovoltaic technology to address the challenge of sustainable powering wireless sensor nodes for Internet of Things (IoTs) and low power consuming electronics. This study reports on new highly electrochemically active PEDOT:PSS (PP) and graphene nanoplatelets (GNPs) composite layer with protruding morphology as counter-electrode for Co(III/II) mediated DSSCs. The PP:GNP counter-electrode layer displays an apparent activation energy (Ea) for charge transfer with Co(bpy)3+/2+ ions of 6.2 kJ•mol−1, almost twofold lower than pristine PP. The fraction of oxidized EDOT units in the polymer increased upon graphene nanoplatelets doping; the work function of PP:GNPs catalyst was best suited to the Co(bpy)3+/2+ redox potential than pristine PP. Despite the significant difference in the catalytic activity, conventional DSSCs with PP and PP:GNP counter-electrodes display similar power conversion efficiency (PCE) of 11.0% and 10.7%, respectively, under 1-Sun illumination. A considerable advantage of the PP:GNP counter-electrode layer emerges under artificial light; DSSCs with PP:GNP cathode render PCE of 29.7% at 1000 lx, surpassing the counterparts with PP counter-electrode. Protruding from the PP matrix film, GNPs particles shorten the effective diffusion path for Cobalt ions and decrease the device resistance; higher photocurrent is possible under low power illumination. Transparency of ca. 65% in the visible region and superior electrical conductivity of the PP:GNP films allow using them in FTO-less bifacial devices; DSSCs with bare soda-lime glass substrates for the cathode displayed a PCE of 9.4% under 1-Sun and 21.9% and 18.7% under 1000 lx, for front and back illumination respectively. This makes PP:GNP counter-electrode very attractive for the cost-effective DSSCs targeting indoor light conversion.

Fabrication of In2O3 functionalized ZnO based nanoheterojunction photoanode for improved DSSC performance through effective interfacial charge carrier separation

This report is to address the limitation of conventional dye-sensitized solar cells (DSSCs) designed using pristine ZnO and N719 dye, which suffers from low performance due to the high charge carrier recombination and the formation of Zn2+-N719 complex over the surface of photoanode. Here we demonstrate the fabrication of ZnO–In2O3 heterojunction based photoanode to extend the charge carrier lifetime by effective interfacial transfer and to boost the light harvesting capacity in dye sensitized solar cells. This opted strategy also helps to prevent the formation dye complex over the photoanode surface. As a result, ZnO–In2O3 heterojunction with optimal composite ratio (1:1) could show better DSSC performance compared to remaining samples when applied as photoanode. Optical analyses and impedance measurements confirmed the enhanced visible light absorption and reduced charge transfer resistance of the composite photoanode due to the modification of ZnO using In2O3 as a counterpart. The results showed that the optimally designed photoanode with superior charge carrier life time and low charge transfer resistance exhibits power conversion efficiency (PCE) of 1.22%, which is nearly 4 times than the pristine ZnO.

CoSe2/graphene composite: a low-cost, high performance counter electrode for dye sensitized solar cells

In this study, Pt-free dye-sensitized solar cells (DSSCs) were fabricated using cobalt selenide (CoSe2)/graphene sheets using facile hydrothermal technique. The Pt free counter electrode (CE) was systematically investigated their physico-chemical properties by using SEM, TEM, XRD, Raman, UV, PL, XPS and BET analysis. Under typical AM 1.5G illumination, the DSSC based on the CoSeSe2 counter electrode achieves a maximum PCE of 12.2 % (Jsc = 22.3 mA/cm2, Voc= 810 mV, and FF= 0.71), which is 5.8 times higher than that of conventional Pt-based DSSC. The improved electro catalytic activity and photo conversion efficiency of the CoSeSe2/graphene CE is due to prevent the recombination of electron-hole pair and extended the visible light absorption of composite samples.

Modifications of Liquid Electrolyte for Monolithic Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSC) has been well known as a highly competitive photovoltaic technology owing to its interesting characteristics, such as, low-cost, simple, and convenient to modify both chemically and physically. One way to reduce the production cost of DSSCs is to conduct a structural modification in the form of a monolithic structure by using a single conductive substrate to accommodate both photoelectrode and counter electrode. However, the photovoltaic performance of monolithic DSSCs is typically still lacking compared to its conventional DSSCs counterparts that uses sandwich structure. One of the crucial factors that determine the photovoltaic performance of a monolithic DSSC is its electrolyte. In this work, the performance of monolithic DSSCs were studied through modifications of the electrolyte component. Two types of commercial liquid electrolytes that have different chemical properties were used and combined into various compositions, and the resulting DSSCs performances were compared. The stability of the monolithic cells was also monitored by measuring the cells repeatedly under the same condition. The result showed that during the first measurement the highest performance with a power conversion efficiency of 1.69% was achieved by the cell with a higher viscosity electrolyte. Meanwhile, the most stable performance is shown by the cell containing lower viscosity electrolyte, which achieved an efficiency of 0.66% that measured on day 35.

Hydrothermally synthesize zinc oxide (ZnO) nanorods as an effective photoanode material for third-generation Dye-sensitized solar cells (DSSCs)

Light scattering and charge transport properties of photoanode can be improved by modifying the morphology of material. In this work, ZnO nanorods have been synthesized via the hydrothermal method. These nanorods have been characterized by Scanning Electron Microscopy (SEM) and X-ray diffraction analysis (XRD). The results indicate that the hydrothermal temperature affects the morphology of nanorods, which eventually influences the photovoltaic performance of devices. The device fabricated with ZnO nanorods photoanode, synthesized at 120 °C, reaches the efficiency of 2.08%, which is superior to conventional ZnO nanoparticles-based DSSC (1.19%).

Binary Redox Couples for Highly Transparent and High-Voltage Dye-Sensitized Solar Cells

The conventional iodine-based (I−/I3 −) electrolyte used in dye-sensitized solar cells (DSSCs) presents several limitations, such as ∼30% absorption of visible light in the wavelength range of 300–500 nm and a large potential difference between the Fermi level of I−/I3 − and the HOMO level of the dye. This has a negative impact on the characteristics of DSSC such as transparency and open circuit voltage (Voc). In the present work, a series of transparent electrolytes are prepared using various additives such as I2, LiI, guanidine thiocyanate/guanidine nitrate (GuSCN/GuNO3), and Br2 to obtain highly transparent and high voltage DSSCs. The results demonstrate that the usage of the optimized electrolyte consisting of 0.003 M Br2, 0.01 M LiI, and 0.1 M GuNO3, with the binary redox couple (I−, Br−)/(I3 −, I2Br−), contributes to an ∼25% increase in transmittance compared to that of the conventional electrolyte, while the concentration of I3 − is significantly reduced. Furthermore, the downward shift in the Fermi level of the binary redox system is shown to provide an ∼100 mV enhancement in the Voc of the DSSC compared with that of the conventional electrolyte based DSSC. In addition, the devices with the optimized binary redox system achieve a power conversion efficiency of ∼7.94% which is closely comparable to the performance of conventional (I−/I3 −) electrolyte-based DSSCs. Thus, the present study could provide immense insights toward the fabrication of high-voltage and transparent DSSCs for the application in transparent photovoltaic windows. Furthermore, by using a binary redox electrolyte, the DSSCs that operative under a 2000 lux compact fluorescent lamp (CFL) were also successfully fabricated and yielded a promising efficiency of 23.6%.

Synergetic effect of a polymer and metalloid composite on the electrocatalytic improvement of dye-sensitized solar cells

Si nanoparticles exhibited significant enhancement on a polymer electrocatalyst and had comparable performance to that of conventional dye-sensitized solar cells.

Facile fabrication of reduced graphene oxide counter electrodes by laser engraver for dye-sensitized solar cell applications

Exploring alternative Pt-free counter electrode with low cost and high electrocatalytic activity is always a main focus at the frontier of dye-sensitized solar cells (DSSCs). In this study, a desktop laser engraver was applied to reduce graphene oxide (GO) film on a fluorine-doped tin oxide (FTO) substrate, and the obtained graphene-based material was further used as counter electrode for DSSC. Additionally, this facile laser-scribing method was also adopted to fabricate a prototype of composite electrode via the combination of reduced graphene oxide (RGO) and carbon black (CB) to enhance the specific surface area and active sites. A variety of characterizations including scanning electron microscopy (SEM), Raman spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were conducted to investigate the microstructures and catalytic properties of these carbon electrodes. The findings reveal that both of the DSSCs with laser-scribed carbon electrodes show evidently increasing photovoltaic performance, and the DSSC based on RGO/CB composite electrode even presents a higher power conversion efficiency (PCE) of 4.49%, comparable to 4.14% of the conventional Pt-based DSSC.

Evaluation and prediction of dye-sensitized solar cells stability under different accelerated ageing conditions

The present paper constitutes one of the few comprehensive studies found in literature on the stability of dye-sensitized solar cells (DSSCs) under different accelerated ageing conditions. Specifically, the accelerated ageing tests involved isothermal ageing at high or low temperature, thermal shock cycling, hydrothermal ageing, and reverse biasing of conventional DSSCs, fabricated using mainly commercially available materials, prepared for DSSCs application. One-diode model was in all cases applied to the characteristic curve of the solar cells, as a simplified version of the general transmission line model used in electrochemical impedance spectroscopy, for the fast and straightforward analysis of the charge transport and back-reaction kinetics in the DSSCs. A semi-analytical model (residual property model (RPM)) that was previously developed by the last author, was also applied, for the first time to solar cells, to predict the degradation of DSSCs performance due to their accelerated ageing. The results showed that moisture, in combination with high temperature, is the most critical environmental factor that leads to the degradation of DSSCs performance. In all cases of accelerated ageing, the stability of the solar cells seemed to be highly dependent on degradation/desorption phenomena of the conventional hydrophilic ruthenium (N719) dye from the TiO2 anode. Finally, it is worth mentioning that the RPM accurately predicted the degradation of DSSCs performance in all cases of accelerated ageing. The present paper reveals a simple but powerful approach for routine evaluation and prediction of the stability of DSSCs and, hopefully, of other solar cell technologies under various accelerated ageing conditions.

Highly efficient, cost-effective counter electrodes for dye-sensitized solar cells (DSSCs) augmented by highly mesoporous carbons

In dye-sensitized solar cells (DSSCs), the electrocatalyst plays a crucial role in the counter electrode as it appreciably influences the overall efficiency of DSSC. The electrocatalyst enhances the rate of the reduction reaction that converts tri-iodide into iodide ions at the counter electrode-electrolyte interface and prevents the recombination of cations in the electrolyte and the photo-generated electrons in the semiconducting material. In any catalytic process, the surface area of the electro-catalyst in the counter electrode determines the number of sites available for interactions between the reactants and the catalyst, and consequently enhances the rate of the reaction. Here, we demonstrate that electrodes based on highly mesoporous carbon (HMC) can serve as inexpensive alternatives to platinum as the electrocatalyst in DSSC. In addition, we report for the first time a systematic investigation of several materials parameters and correlate to their photovoltaic performance. In the DSSCs experiments, the HMCs display high electrocatalytic activity with power conversion (up to 8.77%) which interestingly not only outperforms other reported porous carbons but also outperforms the conventional DSSCs with Pt catalyst.

Ag ion implanted TiO2 photoanodes for fabrication of highly efficient and economical plasmonic dye sensitized solar cells

Materials with tunable optical and photoelectric properties are prerequisite for the development of highly stable, economical and efficient dye sensitized solar cells (DSSCs). In this direction, improved plasmonic DSSCs with comparatively higher light harvesting ability and reduced recombination of photo-generated charge carriers have been fabricated using low energy (120 KeV) Ag ion implanted TiO2 photoanodes at variable fluence. Herein, the origin of improved photovoltaic performance of Ag implanted DSSCs against conventional DSSC has been explained using UV–visible, photoluminescence and kelvin probe measurements. Further, the efficient interfacial charge transportation within Ag implanted DSSCs has been demonstrated through EIS measurements.

WN/nitrogen-doped reduced graphite oxide hybrids for triiodide reduction in dye-sensitized solar cells

The development of low-cost, environmental friendliness, outstanding catalytic activity, superior conductivity and good stability counter electrode (CE) catalyst in dye-sensitized solar cells (DSSCs) is important to promote the commercial application of DSSCs. Here, WN/nitrogen-doped reduced graphite oxide hybrids (WN/NrGO) had been synthesized by hydrothermal method followed by nitridation treatment, which used as CE catalysts for catalyzing I3− to I−. The combined WN and nitrogen-doped reduced graphite oxide (NrGO) into WN/NrGO could effectively regulate the catalytic activity for the reduction of I3−, accelerate the charge transfer at the interface, and then the synergistic effect between of them can be fully achieved. When the WN/NrGO served as the CE catalyst in DSSCs, the photoelectric conversion efficiency (PCE) of 7.42% has been obtained, compared to the conventional Pt-based DSSCs (7.71%). Meanwhile, as-prepared WN/NrGO exhibited higher PCE than that of the solo WN (6.19%) and NrGO (5.81%) in parallel. A series of electrochemical measures revealed that the WN/NrGO displayed the higher catalytic activity and charge transfer ability than that of the solo WN and NrGO, so the synthesized low-cost WN/NrGO have an potential to be used as the effectively CE catalysts for the replacement of the noble Pt.