Controlled Growth Interface of Charge Transfer Salts of Nickel-7,7,8,8-Tetracyanoquinodimethane on Surface of Graphdiyne

Abstract

Open AccessCCS ChemistryRESEARCH ARTICLE25 May 2022Controlled Growth Interface of Charge Transfer Salts of Nickel-7,7,8,8-Tetracyanoquinodimethane on Surface of Graphdiyne Yuxin Liu, Yang Gao, Feng He, Yurui Xue and Yuliang Li Yuxin Liu Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 University of Chinese Academy of Sciences, Beijing 100049 Google Scholar More articles by this author , Yang Gao Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 University of Chinese Academy of Sciences, Beijing 100049 Google Scholar More articles by this author , Feng He Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 University of Chinese Academy of Sciences, Beijing 100049 Google Scholar More articles by this author , Yurui Xue *Corresponding authors: E-mail Address: [email protected]; E-mail Address: [email protected] Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 Science Center for Material Creation and Energy Conversion, School of Chemistry and Chemical Engineering, Institute of Frontier and Interdisciplinary Science, Shandong University, Jinan 250100 Google Scholar More articles by this author and Yuliang Li *Corresponding authors: E-mail Address: [email protected]; E-mail Address: [email protected] Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 University of Chinese Academy of Sciences, Beijing 100049 Google Scholar More articles by this author https://doi.org/10.31635/ccschem.022.202202005 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Here we report an in situ assembly growth method that controls the growth of NiTCNQ on the surface of graphdiyne (GDY). The catalytic system of donor–acceptor–donor (GDY/TCNQ/Ni) structure with multiple charge transfer (CT) was achieved by controlling the growth of NiTCNQ on the surface of GDY. Significantly, a controlled double layer interface of GDY/TCNQ/Ni was formed. This system implemented simultaneously the two elements we expected (1) an incomplete CT, and (2) the infinite distribution of active sites originating from highly asymmetric surface charge distribution. The high conductivity and typical semiconductor characteristics of the catalyst endows it with high catalytic activity. We found that an electrolytic cell consisting of the CT salt as a catalyst provided a 1.40 V ultra-small cell voltage up to 10 mA cm−2 and the outer GDY film effectively prevented the corrosion of the catalyst. Our study is the first to introduce CT complexes to a novel catalytic material platform for high selectivity of catalysts, and undoubtedly demonstrates the high selectivity, stability, and activity of such catalytic systems, which provides a new space for the development of novel conceptual catalysts. Download figure Download PowerPoint Introduction The sustainable hydrogen (H2) production through electrocatalytic overall water splitting (OWS) provides a promising method to overcome the global energy crisis and environmental problems, which is of great significance for industrial and scientific progress.1,2 In terms of hydrogen conversion, precious metal-based materials (e.g., Ru or Ir-based materials for the oxygen evolution reaction (OER); Pt-based materials for the hydrogen evolution reaction (HER)) remain the benchmark catalysts with high catalytic performances, but they are not suitable for large-scale commercialization due to their high cost, low abundance, and insufficient stability. At present, the high cost of precious metals has seriously restricted the development of this field. Transition metal-based materials, such as metal hydroxides, oxides, nitrides, phosphides, carbides, and sulfides, have been extensively studied for anodic OER and cathodic HER.3–6 However, the low catalytic activity of these systems results in sluggish kinetics of OER and HER. In addition, there is no stability advantage of these catalysts. Furthermore, to meet the requirement of industrial alkaline water splitting for hydrogen production, the catalysts should produce large current densities at low cell voltages (e.g., ∼200–400 mA cm−2 at 1.8–2.4 V) and be synthesized from earth-abundant elements to minimize the H2 production cost.7–10 Therefore, to develop catalysts with excellent comprehensive performance, we need to find a new way to produce electrocatalysts with low cost, high activity, and high stability. The unique and excellent structures and properties of graphdiyne (GDY) has triggered extensive investigations on its fundamental properties and potential applications in various research fields, such as catalysis, energy conversion and storage, optical and electrical devices, and so on.11–26 As a new sp- and sp2-cohybridized two-dimensional carbon material, GDY shows large porous structure, high intrinsic activity, excellent electron transfer ability, high electronic conductivity, and high stability.27–29 GDY is an ideal carbon material for synthesizing high-performance catalysts with determined structures and abundant active sites, and provides the opportunities for clearly understanding the relationship of structure and performance. GDY can be grown on arbitrary substrates at low temperatures and ambient pressures, which protects the parent structure and the active site structure from destruction and generates new active sites. 7,7,8,8-Tetracyanoquinodimethane (TCNQ) is a well-known electron acceptor with high electron affinity, which easily reacts with metal atoms to form charge transfer (CT) complexes with high conductivity, high carrier density, and special electron transport properties.30 Metal-TCNQs show excellent electrical and optical properties, and unique and adjustable electron and high CT ability. CT complexes where the CT amount is not an integer is called incomplete CT; it is different from traditional inorganic complexes with an integer CT. Because of their high conductivity and semiconductor characteristics, they have attracted more and more interest in many research fields.31–34 However, until now, research on CT complexes mainly focused on controlled growth, photoelectric devices. and semiconductor properties, while basic and applied research in the field of catalysis remain silent. Recently, we took NiTCNQ–GDY as an example and explored the basis and application of NiTCNQ–GDY as an emerging catalyst in hydrogen energy conversion. In addition, we deeply understand the GDY plays the key role in the generation of efficient catalysts, and find its introduction overcomes important issues such as solvent corrosion, structural instability caused by light or electricity, and poor conductivity.35,36 In this work, we report the successful synthesis of a donor–acceptor–donor (GDY/TCNQ/–Ni) structure with multiple CT by in situ growing GDY layers on the surface of NiTCNQ nanowires (GDY–NiTCNQ). Experimental results demonstrated the incomplete CT and the infinite distribution of active sites originating from highly asymmetric surface charge distribution endow the catalyst with high conductivity, typical semiconductor characteristics, high catalytic activity, and excellent intrinsic properties. These unique and fascinating properties endow GDY–NiTCNQ with excellent catalytic activities toward OER, HER, and OWS. For instance, GDY–NiTCNQ exhibited small overpotentials of 218 and 61 mV at 10 mA cm−2 for OER and HER in 1.0 M KOH. When used as an electrolytic cell, it can drive 10 mA cm−2 at a low cell voltage of 1.40 V. This work provides a new direction toward the development of cost-effective and high-performance electrocatalysts. Experimental Methods Material TCNQ was purchased from Tokyo Chemical Industry (TCI, Shanghai, China). Acetonitrile and methanol were obtained from Concord Technology (Tianjin) Co., Ltd. Nickel foams (NFs) were treated with dilute hydrochloric acid, rinsed with deionized water, and dried with N2 flow before use. Deionized water was purified with a Millipore system. All chemicals were analytical grade and used without further purification unless otherwise specified. Preparation of NiTCNQ in acetonitrile A piece of freshly pretreated nickel film (3 cm × 1.5 cm) was immersed in 10 mM TCNQ acetonitrile solution for 10 min followed by the addition of 3% deionized water at room temperature. After reaction for 6 h, the material was removed from the solution, washed carefully with acetonitrile and water, and dried under the protection of N2. Preparation of GDY on NiTCNQ (GDY–NiTCNQ) A piece of NiTCNQ was immersed in 50 mL acetone solution of hexaethynylbenzene (HEB) at 50 °C under Ar atmosphere protected from light. After reaction for 12 h, the resulting GDY–NiTCNQ was washed with acetone, deionized water, and acetone, followed by drying at 50 °C in a vacuum oven. Characterization The morphology of the material was characterized by scanning electron microscopy (SEM; Hitachi, S 4800; Institute of Chemistry, Chinese Academy of Sciences), transmission electron microscopy (TEM, a JEOL JEM-2100F field-emission high-resolution transmission electron microscope at an accelerating voltage of 200 kV; Institute of Chemistry, Chinese Academy of Sciences), and high-resolution TEM (HRTEM). The energy-dispersive spectroscopy (EDS) mapping analysis was also obtained to characterize the elemental composition of the samples. X-ray diffraction (XRD) measurements were carried out on a PANalytical high-resolution XRD system (EMPYREAN) using Cu Kα radiation (λ = 1.540598 mm). X-ray photoelectron spectroscopy (XPS) was performed on a Thermo Scientific ECSALab 250Xi instrument with monochromatic Al Kα X-ray radiation (Institute of Chemistry, Chinese Academy of Sciences). Electrochemical measurements All electrochemical tests were carried out using an electrochemical workstation (CHI 760E) through a typical three-electrode system, in which the as-prepared samples, graphite rods, and saturated calomel electrode were used as the working electrode, the counter electrode, and the reference electrode, respectively. All the electrolytes used in the experiments were bubbled with Ar for 2 h before use. Linear sweep voltammetry (LSV) measurements were carried out at a scan rate of 2 mV s−1 in 1.0 M KOH solution. Cyclic voltammetry (CV) measurements were carried out at a scan rate of 100 mV s−1. Electrochemical impedance spectroscopy (EIS) was obtained at the frequency range of 100 KHz to 0.1 Hz with a sampling rate of 12 points per decade, and the data obtained was fitted. All potentials were converted to the reversible hydrogen electrode (RHE) according to ERHE = ESCE + E0SCE + 0.059 × pH. X-ray absorption fine structure measurements The X-ray absorption fine structure (XAFS) spectra (Ni K-edge) were collected at 1W1B station in Beijing Synchrotron Radiation Facility (BSRF). The storage rings of BSRF were operated at 2.5 GeV with an average current of 250 mA. Using a Si(111) double-crystal monochromator, the data collection was carried out in transmission/fluorescence mode using an ionization chamber. All spectra were collected in ambient conditions. XAFS analysis and results The acquired extended XAFS (EXAFS) data were processed according to the standard procedures using the ATHENA module implemented in the IFEFFIT software packages. The k3-weighted EXAFS spectra were obtained by subtracting the post-edge background from the overall absorption and then normalizing with respect to the edge-jump step. Subsequently, k3-weighted χ(k) data of Ni K-edge were Fourier transformed to real (R) space using a Hanning windows (dk = 1.0 Å−1) to separate the EXAFS contributions from different coordination shells. To obtain the quantitative structural parameters around central atoms, least–squares curve parameter fitting was performed using the ARTEMIS module of the IFEFFIT software packages. Results and Discussion As shown in Figures 1a and 1b, a two-step in situ growth strategy was used to selectively synthesize the GDY–NiTCNQ catalysts with D–A–D (GDY/TCNQ/Ni) structure, including the first in situ growth of NiTCNQ nanorods and the subsequent growth of the GDY film on the outer layer of the NiTCNQ nanorods that leads to the formation of GDY–NiTCNQ nanowires. Typically, with the dropwise addition of water into the acetonitrile solution of TCNQ, the Ni ions released from the substrate and then interacted with TCNQ forming the A–D (TCNQ–Ni) structure. The NiTCNQ assembled into highly ordered NiTCNQ-nanorods array on the surface of NF.37 The NiTCNQ was then immersed into the acetone solution, after which the HEB precursor was added to grow GDY films on the NiTCNQ surface with the morphology gradually changing from nanorod to nanowire. During this process, the D–A–D (GDY/TCNQ/Ni) structure was formed. Figure 1 | Schematic representation of the controlled synthesis route to the catalytic system of donor–acceptor–donor (GDY/TCNQ/Ni) structures through in situ growth of (a) NiTCNQ nanorods and (b) GDY–NiTCNQ. Download figure Download PowerPoint Figure 2a shows that the color of the samples changed from gray for NF to dark green for NiTCNQ and black for GDY–NiTCNQ during the synthetic process. SEM images clearly show that the smooth surface of 3D NF (Figures 2b–2d) was covered by a film of NiTCNQ nanorods (average diameter, ∼210 nm; Figures 2e–2h). As shown in Supporting Information Figure S1, the NiTCNQ has a flat surface and a fringe lattice spacing of 0.254 nm. The electrostatic potential (ESP) of NiTCNQ (Figure 2h) confirms the interactions between Ni ions and TCNQ with evident CT from Ni to TCNQ, which also demonstrates the formation of the A–D structure. With the growing of GDY on the NiTCNQ surface, the morphology of the nanorods of NiTCNQ changed to nanowires for GDY–NiTCNQ (Figures 2i–2l). As revealed by HRTEM images (Figures 2l and 2m), an obvious shell layer was observed outside of the NiTCNQ core, confirming the successful growth of GDY on the surface of NiTCNQ (Figure 2m). GDY–NiTCNQ exhibits a rough and porous surface, which is beneficial for enlarging the active surface area and the number of active sites. The lattice spacing of the core structure of GDY–NiTCNQ is 0.254 nm ( Supporting Information Figure S2), in accordance with the NiTCNQ, indicating the structure of NiTCNQ was well maintained during the GDY growth process. Scanning TEM (STEM) and EDS mapping images (Figures 2n–2q and Supporting Information Table S1) confirm the presence of carbon, nitrogen, and nickel elements in the GDY–NiTCNQ sample without any impurities. Ni and N are densely distributed in the inner space and sparsely distributed in the edge, and C is evenly distributed throughout the whole material. These results demonstrated the formation of the double layer interface of GDY/TCNQ/Ni, and the GDY film on the outer layer can effectively prevent the catalyst corrosion, which guarantees the long-term stability of the catalyst. Figure 2 | Morphological characterizations of GDY–NiTCNQ and NiTCNQ. (a) Photographs of (i) NF, (ii) NiTCNQ, and (iii) GDY–NiTCNQ. SEM images of (b–d) NF, (e–g) NiTCNQ, and (i–k) GDY–NiTCNQ samples. (h) Electrostatic potential of NiTCNQ. TEM images of (l and m) GDY–NiTCNQ. Elemental mapping images (n–p) of C, Ni, and N atoms in the GDY–NiTCNQ. Download figure Download PowerPoint XRD and XPS measurements were performed to characterize the compositions and structures of the samples. As shown in Figure 3a, the intensity of the peaks for GDY–NiTCNQ decreased as compared with that of NiTCNQ, which might be due to the growth of GDY on NiTCNQ. The XPS survey spectra confirm the presence of Ni, C, and N elements in accordance with the EDS result ( Supporting Information Figures S3 and S4). Compared with pure NiTCNQ (Figure 3b), the C 1s XPS spectra of GDY–NiTCNQ shifted to higher binding energies (BE) by 0.75 eV, revealing the CT from GDY to NiTCNQ. The appearance of an sp-C peak in the C 1s spectra of GDY–NiTCNQ (Figure 3c) indicates the successful growth of GDY on NiTCNQ. Moreover, an independent new peak at 291.96 eV originating from the π–π* shakeup satellite implies the interactions between NiTCNQ and GDY.7 In the Ni 2p region (Figure 3d), the peaks for GDY–NiTCNQ decreased by 1.23 eV as compared with that of NiTCNQ ( Supporting Information Figure S5), revealing the remarkable CT between NiTCNQ and GDY. For GDY–NiTCNQ, the peaks for Ni2+ 2p3/2 and Ni2+ 2p1/2 appear at 856.39 and 873.72 eV, and Ni3+ 2p3/2 and Ni3+ 2p1/2 appear at 858.30 and 875.58 eV, respectively, indicating the presence of the mixed valence states of nickel species. The N 1s (Figure 3e) and O 1s (Figure 3f) peaks of GDY–NiTCNQ located at higher BE than those of pristine NiTCNQ further reveal the presence of electron-transfer in the GDY–NiTCNQ sample.38,39 The Raman ( Supporting Information Figure S6) and Fourier transform infrared (FTIR) ( Supporting Information Figure S7) measurements of the GDY layer were conducted. As shown in Supporting Information Figure S6, pure NiTCNQ spectra features several sharp characteristic peaks. GDY–NiTCNQ exhibits characteristic peaks corresponding to the D-band, G-band, and the vibration of conjugated diine links (2189.8 and 1926.2 cm−1), while the characteristic peaks of NiTCNQ diminished. Moreover, as shown in Supporting Information Figure S7, the FTIR shows the characteristic peak corresponding to GDY, as compared with that of pure NiTCNQ. These results demonstrated the successful growth of GDY on the surface of NiTCNQ. Figure 3 | Structural characterization of GDY–NiTCNQ. (a) XRD spectra of NiTCNQ and GDY-NiTCNQ. XPS spectra for GDY–NiTCNQ and NiTCNQ of (b and c) C 1s, (d) Ni 2p, (e) N 1s, and (f) O 1s. The inset figure in (b) represents the deformation charge density of NiTCNQ. (g) The normalized Co K-edge XANES spectra and (h) the first derivative XANES of GDY–NiTCNQ along with the references. (i) EXAFS spectra of GDY–NiTCNQ at the Co K-edge. Download figure Download PowerPoint Ni K-edge X-ray absorption near-edge structure (XANES) for the samples was performed. Figure 3g shows that the GDY–NiTCNQ exhibits the higher edge energy position than those of NiCl2 and NiO, suggesting the average valence state of nickel in GDY–NiTCNQ is larger than Ni2+. This also implies the mixed valence state of nickel in GDY–NiTCNQ (Figure 3h). The Fourier transforms of the Ni K-edge EXAFS spectrum of GDY–NiTCNQ exhibited a dominant peak at 1.6 Å, which could be assigned to the nearest shell coordination of the Ni–N bond (Figure 3i). The weak peak at 2.5 Å might be attributed to the aggregation of a small number of nickel atoms. The fitted Ni–N coordination number for GDY–NiTCNQ was 4.9 with an average Ni–N bond distance of 2.05 Å ( Supporting Information Table S2), smaller than that of hexa-coordinated NiTCNQ,40 which might be ascribed to the strong interactions between the GDY and NiTCNQ species. The obviously enhanced CT ability at the double layer interfaces of GDY/TCNQ/Ni was expected to endow the catalyst with incomplete CT and the infinite distribution of active sites originating from highly asymmetric surface charge distribution. The significantly increased number of active sites would further accelerate CT and lower energy barriers of the reaction. These are all beneficial to improve the catalytic activity of the catalysts. The OER catalytic performances of the samples were studied using a three-electrode system by testing LSV in O2-saturated 1.0 M KOH solution at the scan rate of 2 mV s−1. All polarization curves were corrected by the iR-compensation. NiTCNQ, NF, and RuO2 were also tested in the same conditions for reference. As shown in Figure 4a, the anodic peak appearing in the range of 1.3–1.4 V versus RHE referred to the nickel oxidation from Ni(II) to Ni(III), and the following peak represented the OER catalytic activity. GDY–NiTCNQ showed the best OER activity with the smallest overpotential of 218 mV at 10 mA cm−2 compared with pure NiTCNQ (343 mV) and commercial RuO2 (282 mV). Moreover, GDY–NiTCNQ exhibited a lower Tafel slope of 65.92 mV dec−1 than NiTCNQ (95.22 mV dec−1), NF (250.78 mV dec−1), and RuO2 (96.93 mV dec−1), indicating it facilitated the reaction kinetics for OER evolution (Figure 4b). For further evaluation of the OER activity, the turnover frequency (TOF) value was calculated. At the overpotential of 400 mV, GDY–NiTCNQ displayed a higher TOF value of 3.82 s−1 than NiTCNQ (0.82 s−1), NF (0.06 s−1), and most of the reported electrocatalysts ( Supporting Information Table S3). Figure 4 | OER and HER performances. (a) Polarization curves of GDY-NiTCNQ, NiTCNQ, NF and RuO2 for OER at the scan rate of 2 mV s−1. (b) Corresponding Tafel slopes of the samples for OER. (c) Polarization curves of GDY–NiTCNQ obtained before and after 9,000 OER CV cycles. (d) O 1s XPS spectra of GDY–NiTCNQ after OER cycling tests. (e) Ni 2p XPS spectra and (f) the percentages of Ni2+ species of GDY–NiTCNQ obtained after OER cycling tests. (g) Polarization curves of GDY-NiTCNQ, NiTCNQ, NF, and 20 wt. % Pt/C for HER at the scan rate of 2 mV s−1. (h) Corresponding Tafel slopes of the materials for HER. (i) Polarization curves of GDY–NiTCNQ obtained before and after 2500 HER CV cycles. (j) O 1s XPS spectra, (k) Ni 2p XPS spectra, and (l) the percentages of Ni2+ species in GDY–NiTCNQ samples. Download figure Download PowerPoint Long-term stability of the catalyst is of great significance for practical applications. As shown in Supporting Information Figure S8, GDY–NiTCNQ maintained its catalytic activity for 160 h under continuous electrolysis at ∼50 mA cm−2, revealing its long-term stability ( Supporting Information Figure S8). GDY–NiTCNQ also displayed a negligible decrease in catalytic activity during the continuous CV tests for 9000 cycles (Figure 4c). The morphologies of the GDY–NiTCNQ catalysts after the stability tests, characterized by SEM ( Supporting Information Figure S9) and TEM ( Supporting Information Figure S10), showed no aggregations formed and the nanorod morphology was well retained, demonstrating the high stability of the as-prepared catalysts. Ex situ XPS tests were employed on GDY–NiTCNQ to determine the structural evolution during the continuous cycling tests. The O 1s XPS spectra showed two new peaks at 530.90 (hydroxyl group) and 529.4 eV (the lattice oxygen in metal oxycompounds) appeared after the cycling tests (Figure 4d). It was also found that the position of the Ni 2p peak shifted to lower BE and the proportion of the Ni2+ species increased gradually during the catalysis (Figures 4e and 4f). Finally, the proportion of Ni2+ eventually stabilized at about 82%. Obviously, these results confirm the generation of the oxycompounds was closely associated with the content of Ni2+ in OER processes, which play a key role in the high-efficiency 4e− oxygen electrocatalysis.41,42 The HER catalytic activity of GDY–NiTCNQ was further tested in 1.0 M H2-saturated KOH solution. Figure 4g shows the LSV curves of samples: GDY–NiTCNQ exhibited a small overpotential of 61 mV at 10 mA cm−2, which was smaller than NiTCNQ (116 mV) and NF (165 mV), and close to the noble catalyst Pt/C (32 mV). The corresponding Tafel slopes of GDY–NiTCNQ, NiTCNQ, NF, and Pt/C were 114.64, 215.47, 262.75, and 22.75 mV dec−1, respectively (Figure 4h). The TOF values for GDY–NiTCNQ, NiTCNQ, and NF were 0.32, 0.27, and 0.11 s−1, respectively, at the overpotential of 100 mV. All above results indicated the obvious enhancement of HER activity. Moreover, there was only a negligible change in current density after 2500 cycles, indicating the catalyst’s high stability (Figure 4i). The morphologies of the GDY–NiTCNQ catalysts after the HER tests ( Supporting Information Figure S11 for SEM; Supporting Information Figure S12 for TEM) were well retained, demonstrating the high stability of the as-prepared catalysts. To reveal the origin of the catalytic activity, the in situ XPS measurements were conducted. As shown in Figure 4j, new peaks corresponding to the hydroxyl species were observed at 530.9 eV in the O 1s XPS spectra as compared with the as-prepared catalysts. The ratio of Ni2+ decreased continuously as the HER proceeded (Figures 4k and 4l), implying the continuous increase of mean value state of nickel element, which might be the origin of degradation of HER activity. For the further determination of the activity of GDY–NiTCNQ, EIS Nyquist plots were recorded to verify the CT behavior. The parameters obtained were fitted with R(QR)(QR) equivalent circuit featuring solution resistance (Rs), CT resistance (Rct), and absorption resistance (Rab) to fit the Nyquist plots (Figure 5a). GDY–NiTCNQ exhibited the lowest values of Rs(3.63 Ω) and Rct (0.1312 Ω) compared with NiTCNQ (Rs = 4.52 Ω, Rct = 1434 Ω) and NF (Rs = 4.98 Ω, Rct = 9.05 Ω), which indicated the highest conductivity and facilitated proton transfer process. The electrochemical active surface area was also evaluated through electrical-double layer capacitance (Cdl) measured under various scan rates of CVs (Figure 5b and Supporting Information Figure S13). GDY–NiTCNQ showed a larger Cdl of 4.68 mF cm−2 than NiTCNQ (2.79 mF cm−2) and NF (2.72 mF cm−2), indicating the larger surface area and higher surface roughness assigned to the introduction of GDY. Based on both robust OER and HER performance, GDY–NiTCNQ was used as both anode and cathode in a two-electrode setup for OWS. The catalytic system exhibited high OWS performance with a low cell voltage of 1.40 V to afford 10 mA cm−2, much lower compared with those electrolyzers like NiTCNQ||NiTCNQ (1.422 V) (Figure 5c), and the other reported state-of-the-art catalysts, including [email protected] (1.56 V at 10 mA cm−2), [email protected]/1 (1.69 V at 10 mA cm-2), V-CoP (1.59 V at 10 mA cm−2), and so on (Figure 5d and Supporting Information Table S4). During the OWS test, continuous bubbles of H2 and O2 were generated rapidly from the cathode and anode, respectively (Figure 5e). The good catalytic performance in OWS in basic electrolyte demonstrates the promising prospects in practical applications of GDY–NiTCNQ. Figure 5 | Electrochemical properties and OWS performance. (a) Nyquist plots of samples in 1.0 M KOH solution. Inset: Equivalent circuit model for EIS analysis, and the fitting model is R(QR)(QR). (b) The capacitive at 0 V (versus SCE) of scan rates for samples. (c) OWS performance of the electrocatalyst. (d) OWS activities of GDY–NiTCNQ and previously reported electrocatalysts. (e) The practical water electrolyzer in a working condition. Download figure Download PowerPoint Conclusion We report an in situ assembly growth method that controls the growth of NiTCNQ on the surface of GDY, leading to the selective formation of a unique D–A–D (GDY/TCNQ/Ni) structure with multiple CT. In such catalytic systems, the amount of CT between donor and acceptor is <1, that is, incomplete CT between donor and acceptor. Such surface charge distribution greatly increases the number of active sites and intrinsic activity of the catalytic system, thereby realizing a new concept for increasing the activity of the catalytic system through incomplete CT between the D–A. The experimental results show that the complex formed by incomplete CT demonstrates excellent electrical conductivity and typical semiconductor characteristics, leading to the high catalytic activity of such a catalytic system in OER, HER, and OWS. We found that an electrolytic cell consisting of the CT salt as a catalyst provided a 1.40 V ultra-small cell voltage up to 10 mA cm−2. Another outstanding effect is that the outer GDY film effectively prevented the corrosion of the catalyst, which is greatly conducive to its long-term stability. This work provides a new way to selectively prepare novel catalysts with high selectivity, activity, and stability. Supporting Information Supporting Information is available includes the details for the calculation of turnover frequencies (TOFs), Figure S1–S13, and Table S1–S4. Conflict of Interest There is no conflict of interest to report. Funding Information This research was made possible by a generous grant from the National Key Research and Development Project of China (no. 201