MXene supported PtCo bimetallic catalyst for hydrogen evolution in acidic conditions

Abstract

Using the electrochemical technology to split water molecules to produce hydrogen is the key to obtain green hydrogen for solving the energy crisis. The large-scale application of hydrogen evolution reaction (HER) in water dissociation requires a highly active catalyst. In this paper, the highly dispersed PtCo bimetallic nanoparticles loading on MXene (PtCo/MXene) were prepared by using a step-to-step reduction strategy. The mentioned PtCo/MXene catalyst exhibits a high current density of −100 mA/cm² in an acidic medium with just a 152 mV overpotential. In addition, the PtCo/MXene catalyst also displays a superior stability. Computational analysis and experimental testing demonstrate that the electronic interaction between Pt and Co can effectively modify the electronic structure of the active site, thereby enhancing the inherent catalytic performance of the material. More importantly, MXene two-dimensional nanosheets can expose more active sites because of their large specific surface area. Furthermore, MXene substrate with excellent electrical conductivity and harmonious interfaces between PtCo and MXene enhance charge transfer efficiency and lower the reaction activation energy.

Graphical abstract

Keywords

MXene / PtCo bimetallic / hydrogen evolution reaction (HER)

1 Introduction

Recently, the global community has been confronted with simultaneous energy and environmental crises. Hydrogen energy is considered to be a promising solution due to its high energy density and zero pollutant emissions [1–3]. Currently, hydrogen is mainly obtained through the cracking of fossil fuels, which increases energy consumption and emissions of greenhouse gases, thus undermining the achievement of carbon neutrality goals [4,5]. Utilizing renewable energy for electrochemical water splitting is an eco-friendly and sustainable method to generate hydrogen [6–8]. To improve hydrogen production efficiency and reduce energy consumption, it is imperative to identify a highly effective catalyst for the hydrogen evolution reaction (HER). Platinum (Pt) group elements are commonly employed as HER catalysts due to their exceptional intrinsic catalytic prowess [9–12]. However, widespread implementation has been constrained by the scarcity and high expense of these resources [13]. Raising the utilization rate of metal atoms to develop low content of Pt catalysts is very important and valuable [14,15].

Recently, supported catalysts have been developed. These approaches aim to minimize the precious metal content while preserving its exceptional reactivity. For example, Liu et al. [16] loaded Pt single atoms onto onion-like carbon nanospheres, and Park et al. [17] incorporated Pt single atoms onto two-dimensional (2D) transition metal borides (MBenes), in which the catalytic activity is maintained while the Pt content is effectively reduced. Nonetheless, the stability of single-atom catalysts is inadequate due to their high surface entropy. In this case, Li et al. [18] loaded Pt nanoparticles onto a spongy MoS₂/N-doped carbon composite (Pt-MoS₂/CN) for HER, but the load content of Pt was high. Recently, the preparation of bimetallic material systems can not only reduce the amount of precious metals by improving the metal utilization rate of precious metals but also improve the HER activity of materials by optimizing the electron cloud state of the active site [19–23]. For instance, Zhang et al. [24] synthesized uniform assemblies of Pt₇₅Co₂₅ nanodendrites. The chemical bonding and electron transfer interactions between Pt and Co endowed the material with excellent stability and activity, particularly under acidic conditions. In another study, Yu et al. [25] immobilized PtCo nanoparticles onto N-doped carbon carriers, with the observed interaction between Co and Pt contributing to enhanced catalytic activity. Furthermore, MXene materials primarily encompass a family of 2D MBenes carbides, or carbon nitrides, characterized by the chemical formula M_nX_n−1T_x (where M represents the transition metal atom; X is either C or N; n can be 2, 3, or 4; and T_x denotes −O, −OH, or −F) [26,27]. Because of the its layered nanostructures, high conductivity, excellent hydrophilicity, good mechanical stability, and rich surface chemical properties, MXene is widely used in the field of catalysis [28–32]. Therefore, in the MXene substrate load, double metal materials can provide an effective strategy, to reduce the content of precious metals, and at the same time, improve the catalytic performance.

Herein, a step-to-step reduction method is used to load PtCo bimetallic catalysts on Ti₃C₂T_x MXene substrate. This synthesis strategy can expose Pt metal atoms to the surface, and the introduction of Co optimizes the electron cloud state of Pt. Besides, coupling bimetallic PtCo with 2D MXene substrates with a good electrical conductivity will enhance surface area significantly and minimize charge transfer resistance. Further, electrochemical experiments and density functional theory (DFT) calculations show that PtCo bimetallic nanoparticles loading on MXene (PtCo/MXene) promotes the desorption of H* and increases HER activity in acidic media. The PtCo/MXene obtained exhibits an exceptional HER performance with a low overpotential of 60 and 152 mV at current densities of −10 and −100 mA/cm², respectively, and a remarkable working stability in 0.5 mol/L H₂SO₄ solution.

2 Experimental section

2.1 Preparation of Ti₃C₂T_x MXene nanosheets

Ti₃C₂T_x MXene was synthesized according to the selective etching of aluminum layers from the Ti₃AlC₂ MAX phase [33]. Briefly, 3.2 g of LiF is dissolved in a Teflon beaker containing 50 mL of HCl aqueous solution (12 mol/L) and continuously stirred for 5 min to completely dissolve. Afterward, 3.2 g of Ti₃AlC₂ was gradually and slowly added to the above mixture solution within 10 min and then kept at 45 °C for 24 h under stirring. The mixture was subsequently washed and centrifuged with ultrapure water repeatedly until the pH of the supernatant stabilized around 6‒7. The resulting precipitate was redispersed in 80 mL of ultrapure water and subjected to sonication for 1 h at a nitrogen atmosphere. Finally, the homogeneous monolayer Ti₃C₂T_x MXene suspension was collected by centrifugation at 3500 r/min for 30 min. The as-synthesized Ti₃C₂T_x MXene suspension (about 10 mg/mL) was preserved in a refrigerator at 3 °C.

2.2 Preparation of PtCo/MXene, Pt/MXene, and Co/MXene

Ten milliliters of MXene (10 mg/mL) were dissolved in 20 mL of ultrapure water and kept stirring. Then, 1.0 mL of Co(NO₃)₂·6H₂O aqueous solution (72 mmol/L) was added to the above solution. After stirring for 1 h, 1 mL of NaBH₄ (2 mol/L) was added to the mixture and stirred for 1h. Subsequently, 3.0 mL of 1 mmol/L H₂PtCl₆ aqueous solution was incorporated into the above mixture, followed by continuous stirring for 1 h at room temperature. Subsequently, 1 mL of 2 mol/L NaBH₄ was injected into the mixture and stirred for 1 h. Eventually, the bimetallic Pt-Co catalyst supported by MXene (PtCo/MXene) was collected via centrifugation, followed by multiple washings with ultra-pure water, and overnight freeze-drying. Different proportions of Pt_xCo_y/MXene materials were prepared by adjusting the amount of Co and Pt precursor. The preparation procedures of Pt/MXene and Co/MXene catalysts were similar to those of PtCo/MXene, except for introducing the monometallic Pt or Co species.

2.3 Materials characterization

The X-ray diffraction (XRD) data acquired from the Bruker D8 Advance instrument with the Cu Kα radiation was used to explore the crystal structure. The microstructure and morphology of the materials were observed via scanning electron microscopy (SEM) on FEI Tecnai G2 F30 microscope, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive spectroscopy (EDS) on FEI Tecnai G2 F20 electron microscope. The elemental valence information of the materials was examined by X-ray photoelectron spectroscopy (XPS) on an X-ray photoelectron spectrometer (Thermo Scientific K-Alpha + ) with Al Kα X-rays.

2.4 Electrochemical measurements

All electrochemical activity tests of HER were conducted in a three-electrode cell with an electrochemical workstation (CHI 660E, CH Instruments) equipped with 0.5 mol/L of H₂SO₄ at room temperature. A 1 cm × 2 cm carbon paper was used as the working electrode (WE), saturated calomel and graphite rod as the reference electrode (RE) and counter electrode (CE), and 0.5 mol/L of H₂SO₄ as the electrolyte. To prepare the WE, 20 mg of prepared catalyst, 50 μL of Nafion (5 wt.%, mass fraction), 500 μL of ethanol and 450 μL of ultrapure water were mixed and ultrasonicated for about 1 h to obtain the homogeneous ink. Afterward, 100 μL of catalyst slurry was taken and coated on the carbon paper (1 cm × 1 cm) with a loading capacity of 2.0 mg/cm², which was used as the WE when dried in air.

For HER tests, linear sweep voltammetry (LSV) was used to measure the polarization curve at a scan rate of 5 mV/s. Before the LSV testing, the catalyst was stabilized by cycling 10 times cyclic voltammetry (CV) at a scan rate of 100 mV/s. The Tafel diagram is obtained by calculating and fitting the LSV polarization curve. Electrochemical impedance spectroscopy (EIS) was conducted by applying an AC voltage with an amplitude of 10 mV across a frequency range from 100 kHz to 0.01 Hz at a potential of −200 mV vs. the reversible hydrogen electrode (RHE). The electrochemically active surface area (ECSA) was calculated based on the electrochemical double-layer capacitance (C_dl). The C_dl was determined through conventional CV measurements conducted at various scan rates within the non-Faraday region. The CV curves were acquired within the voltage range of 0.4‒0.5 V vs. RHE at different scan rates ranging from 20 to 100 mV/s. The cycling stability was assessed by CV conducted between 300 and −100 mV vs. RHE at 100 mV/s and the chronopotentiometry measurement at a constant current density of 10 mA/cm².

All potentials were converted to RHE scale according to the Nernst equation E(RHE) = 0.242 + 0.059 × pH + E(SCE), and the current densities were normalized to the geometric surface area. All polarization curves were performed with an iR-compensation correction of 95%.

2.5 DFT calculation methods

In this study, the functionalities for visualization, modeling, structural optimization, and energy calculations were facilitated by the Device Studio (DS) program. All calculations, adhering to DFT, were executed utilizing the DS-PAW software integrated into the DS [34–36]. The electronic exchange-correlation energy was represented by the Perdew−Burke−Ernzerhof generalized gradient approximation (PBE-GGA) [37]. The interaction between ionic cores and valence electrons was described by the projector-augmented-wave (PAW) method. The cut-off value of the plane wave kinetic energy was set to 500 eV. The convergence criterion for structural optimization is that the atomic force is less than 0.01 eV/Å and the energy is less than 1 × 10⁻⁵ eV. A Co model with (102) surface was established, which was the 1 × 2 × 1 supercell (including 42 atoms) after the structure optimization and it had a 15 Å vacuum layer to avoid interactions between periodic images. A 4 × 7 × 1 k-mesh grid was used to integrate the Brillouin region. The Gibbs free energy for H* adsorption on PtCo (\mathrm{\Delta }{G}_{{\text{H}}^{\ast }}) was calculated by

(1)\mathrm{\Delta }{G}_{{\text{H}}^{\ast }}=E_{\text{total}}-E_{\text{PtCo}}-\frac{E_{{\text{H}}_{\text{2}}}}{2} +\mathrm{\Delta }{E}_{\text{ZPE}}-T \mathrm{\Delta }{S}_{\text{H}},

where E_total is the total energy of H adsorbing on the catalysts, E_{\text{PtCo}} is the energy of pure PtCo, and H₂ energy is E_{{\text{H}}_{\text{2}}}, \mathrm{\Delta }{E}_{\text{ZPE}} represents the difference in zero-point energy between the gas phase and the adsorbed state, and ∆S_H is the changes in entropy.

3 Results and discussion

The synthesis and preparation process of PtCo/MXene are shown in Fig.1. First, the Ti₃C₂T_x MXene 2D nanosheets were prepared by conducting selective etching of Al element in Ti₃AlC₂ MAX phase with LiF-HCl and subsequent ultrasonic treatment. Then, the PtCo/MXene catalyst was prepared by utilizing the step-by-step reduction method. Briefly, Co cation was first deposited on the surface of Ti₃C₂T_x MXene and reduced by the NaBH₄ aqueous solution, and then Pt species was added and reduced by the NaBH₄ aqueous solution. This stepwise reduction method could fully expose the precious metals to the outer surface of the bimetal and improve the electronic state between the two metals, Co and Pt.

The SEM image of the material is displayed in Fig.2(a) and Fig.2(b), and the PtCo/MXene material obtained is composed of 2D nanosheets stacked. The expansive specific surface area of 2D nanosheets facilitates the exposure of active sites and the diffusion of reactants. Figure S1 in the Electronic Supplementary Material (ESM) illustrates the nitrogen adsorption-desorption isotherms and pore size distributions of Ti₃C₂T_x MXene and PtCo/MXene. The Brunauer−Emmett−Teller (BET) surface area for Ti₃C₂T_x MXene and PtCo/MXene is reported as 12.36 and 20.82 m²/g, respectively (Table S1). From the TEM image of Fig.2(c), it can be noticed that the size of PtCo/MXene 2D nanosheets is about 2 μm. As displayed in Fig.2(d), the PtCo nanoparticles were dispersed on the MXene substrate, and the average side length of PtCo nanoparticles is about 3 nm. As shown in the HRTEM image in Fig.2(e) and 2(f), the lattice stripe spacing with 0.26 nm corresponds to (100) crystal faces of Ti₃C₂T_x MXene [30], and the lattice spacing with 0.217 nm corresponds to (100) crystal faces of PtCo nanoparticles [38]. HAADF-STEM images and the EDS element mapping of the PtCo/MXene are shown in Fig.2(h)–2(k), in which the elements of Co, Pt, Ti, and C are evenly distributed in the sample of PtCo/MXene, and the atoms of Pt and Co appear in overlapping positions, indicating that the Pt and Co element are in close contact with the Ti₃C₂T_x MXene support, and the bimetal Pt–Co is formed.

The XRD patterns of Ti₃C₂T_x MXene, Ti₃AlC_2, PtCo/MXene, Pt/MXene, and Co/MXene are shown in Fig.3(a) and 3(b). The three typical peaks of the Ti₃AlC₂ phase at 9.8°, 39.1°, and 42.3° represent its (002), (104), and (105) crystal faces, respectively. The Ti₃C₂T_x MXene obtained after LiF-HCl etching and ultrasonic stripping only shows its (002) plane peak at 8.6°. This angle deviation could be attributed to the enlargement of the crystal face distance in Ti₃C₂T_x MXene and the removal of the Al atomic layer [39]. No diffraction peaks corresponding to Pt or Co species were observed in the XRD patterns of PtCo/MXene, Pt/MXene, and Co/MXene, which may be attributed to the low content of Pt or Co species. The loading of Pt and Co in the three samples was assessed via an inductively coupled plasma atomic emission spectrometer (ICP-AES) analysis. As presented in Table S2, the Pt loadings for PtCo/MXene and Pt/MXene are 0.43 and 0.44 wt.%, respectively. The Co loadings in PtCo/MXene and Co/MXene are 3.82 and 3.84 wt.%, respectively. These values are similar to theoretical metal loads, suggesting successful anchorage of most metal precursors onto the MXene support. To determine the valence states and surface chemical environment of the sample elements obtained, PtCo/MXene, Pt/MXene, and Co/MXene were characterized by XPS. As displayed in Fig.3(c), the two peaks at the binding energy of 71.1 and 74.4 eV are attributed to Pt 4f_7/2 and Pt 4f_5/2, respectively. The results show that the valence states of Pt species in Pt/MXene are close to that of metallic Pt [40–42]. The binding energies of Pt 4f_7/2 and Pt 4f_5/2 in PtCo/MXene are 71.6 and 74.9 eV respectively, which are the positive shifts of 0.5 eV compared with Pt/MXene. It can be noticed that the binding energy signals at 797 and 781.4 eV are assigned to Co 2p_1/2 and Co 2p_3/2 in Co /MXene (Fig.3(d)), indicating that the valence state of the Co species is mainly +2 [40]. The binding energies of Co 2p_1/2 and Co 2p_3/2 in the Co 2p region of PtCo/MXene are 796.5 and 780.9 eV, respectively, which are the negative shifts of 0.5 eV compared with Co/MXene. Based on the information given, electrons might be transferred from the Pt atom to the Co atom in the created PtCo/MXene substance. This supports the presence of a Pt−Co bimetallic compound and the occurrence of an interaction between them.

The evaluation of HER electrocatalytic performance was conducted for PtCo/MXene, Pt/MXene, Co/MXene, and Ti₃C₂T_x MXene in 0.5 mol/L of H₂SO₄ at room temperature, using a standard three-electrode system. The LSV curve of the HER (Fig.4(a)) shows that the overpotential of PtCo/MXene is only 60 and 152 mV at the current density of −10 and −100 mA/cm², which is significantly smaller than those of the Pt/MXene (47 mV at −10 mA/cm² and 194 mV at −100 mA/cm²), Co/MXene (284 mV at −10 mA/cm² and 464 mV at −100 mA/cm²) (Fig.4(b)). The HER catalytic activity of the material approaches the forefront of performance among current Pt-based catalysts [43]. The Tafel diagram was obtained by linear fitting of the LSV curve to characterize the HER kinetics of the catalysts. As shown in Fig.4(c), the Tafel slope of PtCo/MXene is only 42 mV/dec, which is lower than those of the Pt/MXene (45 mV/dec), Co/MXene (201 mV/dec), and MXene (207 mV/dec), further suggesting a faster HER intrinsic reaction kinetic. The HER activity of PtCo/MXene was further evaluated by EIS. The EIS was tested by applying an AC voltage with an amplitude of 10 mV over a frequency range of 100 kHz to 0.01 Hz at a potential of −200 mV vs. RHE. The Nyquist plots suggest that the charge-transfer resistance (R_ct) of PtCo/MXene is 0.88 Ω, significantly lower than Pt/MXene (1.26 Ω) and Co/MXene (26.94 Ω) (Fig.4(d)). This shows that the prepared PtCo/MXene can provide a fast charge transfer rate during electrocatalysis. Several catalytic systems featuring different substrates were introduced as comparable groups. Notably, PtCo/MXene exhibited the highest electrocatalytic activity for the HER, as depicted in Fig. S2. To show that the PtCo/MXene catalytic material prepared has more active sites, the electrochemically active surface areas were determined based on the double-layer capacitance (C_dl) derived from CV [44]. The C_dl value of PtCo/MXene is 22.78 mF/cm², which is much larger than those of the Pt/MXene (17.70 mF/cm²) and Co/MXene (14.37 mF/cm²) (Fig.4(e) and S3). For an outstanding HER catalyst, it is crucial to possess not only an excellent catalytic activity but also a long-term stability. CV cycles and chronopotentiometry were used to evaluate the cyclic stability of catalysts in the 0.5 mol/L H₂SO₄, respectively. It was shown that the LSV curve of the PtCo/MXene catalyst did not change significantly after 1000 CV cycles, and the overpotential rose from 152 to 164 mV at a current density of −100 mA/cm². A chronopotentiometry test was conducted at a current density of −10 mA/cm², and 86% of the initial value was maintained after 24 h (Fig.4(f)), indicating that PtCo/MXene has a high catalytic stability in acidic electrolytes.

To further understand the catalytic activity of the PtCo/MXene and enable the catalyst to have an excellent HER performance with a lower Pt load, the Pt_xCo_y/MXene catalyst with different Pt−Co atomic ratios was prepared. The LSV curve of the HER catalysts obtained is shown in Fig.5(a) and 5(b), when the atomic ratio of Pt and Co is 4 to 96, it has a lower hydrogen evolution overpotential. Pt₄Co₉₆/MXene also has the lowest charge transfer impedance (Fig.5(c)) and Tafel slope (Fig.5(d)). The catalyst performance of different Pt−Co ratios is different, which may be mainly because the low content of Co is not conducive to the interaction between Co and Pt, while the high content of Co will cover a certain active site of Pt.

To further illustrate the outstanding HER performance of PtCo/MXene in acidic conditions, DFT calculations were performed based on material characterization utilizing DS-PAW software integrated with the DS [36]. The correlative structure models of the PtCo bimetals and Co monometals are shown in Fig.6(a). Based on the surface HER process established, the adsorption energy of H* in acidic media is calculated. As shown in the H* adsorption energy in Fig.6(b), the Co monometallic possesses a relatively negative H* adsorption free energy of −0.16 eV, suggesting a substantial potential barrier in the H desorption process during H₂ formation. In contrast, the H* adsorption-free energy of PtCo bimetals is closer to 0 eV (−0.14 eV), which enhances the desorption of H* for rapid H₂ formation. These results indicate that PtCo bimetal is more favorable to the HER process under acidic conditions.

4 Conclusions

In summary, a step-by-step reduction approach was used to fabricate small and highly dispersed PtCo bimetallic catalysts on MXene. The introduction of Co species changed the electronic structure of the active site and promoted the catalytic performance of Pt precious metal in HER. The PtCo/MXene obtained has a superior HER activity with a low overpotential of 60 and 152 mV at current densities of −10 and −100 mA/cm², respectively, and excellent working durability in the 0.5 mol/L H₂SO₄ medium. A series of experimental results and characterization show that PtCo/MXene materials possess a considerable specific surface area and minimal charge transfer impedance. The DFT calculation shows that PtCo bimetal can promote the desorption of H* and promote the HER process in an acidic medium. This work provides a valuable perspective to introduce low-load precious metals on MXene and guarantee its activity and stability.

References

[1] Roger I, Shipman M A, Symes M D. Earth-abundant catalysts for electrochemical and photoelectrochemical water splitting. Nature Reviews Chemistry, 2017, 1: 0003

[2] Jin H, Wang X, Tang C. . Stable and highly efficient hydrogen evolution from seawater enabled by an unsaturated nickel surface nitride. Advanced Materials, 2021, 33(13): 2007508

[3] Wang T, Tao L, Zhu X. . Combined anodic and cathodic hydrogen production from aldehyde oxidation and hydrogen evolution reaction. Nature Catalysis, 2022, 5(1): 66–73

[4] Abdalla A M, Hossain S, Nisfindy O B. . Hydrogen production, storage, transportation and key challenges with applications: A review. Energy Conversion and Management, 2018, 165: 602–627

[5] Megía P J, Vizcaíno A J, Calles J A. . Hydrogen production technologies: From fossil fuels toward renewable sources. A mini review. Energy & Fuels, 2021, 35(20): 16403–16415

[6] Peng H, Zhou K, Jin Y. . Hierarchical nanostructure with ultrafine MoO₃ particles-decorated Co(OH)₂ nanosheet array on Ag nanowires for promoted hydrogen evolution reaction. Chemical Engineering Journal, 2022, 429: 132477

[7] Yang C, Zhong W, Shen K. . Electrochemically reconstructed Cu-FeOOH/Fe₃O₄ catalyst for efficient hydrogen evolution in alkaline media. Advanced Energy Materials, 2022, 12(16): 2200077

[8] Shiva Kumar S, Himabindu V. Hydrogen production by PEM water electrolysis—A review. Materials Science for Energy Technologies, 2019, 2(3): 442–454

[9] Li L, Yu D, Li P. . Interfacial electronic coupling of ultrathin transition-metal hydroxide nanosheets with layered MXenes as a new prototype for platinum-like hydrogen evolution. Energy & Environmental Science, 2021, 14(12): 6419–6427

[10] Wang J, Han L, Huang B. . Amorphization activated ruthenium−tellurium nanorods for efficient water splitting. Nature Communications, 2019, 10(1): 5692

[11] Fan J, Wu J, Cui X. . Hydrogen stabilized RhPdH 2D bimetallene nanosheets for efficient alkaline hydrogen evolution. Journal of the American Chemical Society, 2020, 142(7): 3645–3651

[12] Zhou K, Wang Z, Han C. . Platinum single-atom catalyst coupled with transition metal/metal oxide heterostructure for accelerating alkaline hydrogen evolution reaction. Nature Communications, 2021, 12(1): 3783

[13] Bai Y, Liu Y, Liu M. . Near-equilibrium growth of chemically stable covalent organic framework/graphene oxide hybrid materials for the hydrogen evolution reaction. Angewandte Chemie, 2022, 134(2): e202113067

[14] Guo C, Jiao Y, Zheng Y. . Intermediate modulation on noble metal hybridized to 2D metal-organic framework for accelerated water electrocatalysis. Chem, 2019, 5(9): 2429–2441

[15] Ye S, Luo F, Xu T. . Boosting the alkaline hydrogen evolution of Ru nanoclusters anchored on B/N-doped graphene by accelerating water dissociation. Nano Energy, 2020, 68: 104301

[16] Liu D, Li X, Chen S. . Atomically dispersed platinum supported on curved carbon supports for efficient electrocatalytic hydrogen evolution. Nature Energy, 2019, 4(6): 512–518

[17] Park S J, Nguyen T H, Tran D T. . Delaminated MBene sheets beyond usual 2D transition metal materials for securing Pt single atoms to boost hydrogen evolution. Energy & Environmental Science, 2023, 16(9): 4093–4104

[18] Li L, Wang X, Li J. . One-pot synthesis of ultrafine Pt-decorated MoS₂/N-doped carbon composite with sponge-like morphology for efficient hydrogen evolution reaction. Journal of Alloys and Compounds, 2021, 872: 159562

[19] Tan S, Ouyang W, Ji Y. . Carbon wrapped bimetallic NiCo nanospheres toward excellent HER and OER performance. Journal of Alloys and Compounds, 2021, 889: 161528

[20] Pan Q, Xu C, Li X. . Porous Ni–Mo bimetallic hybrid electrocatalyst by intermolecular forces in precursors for enhanced hydrogen generation. Chemical Engineering Journal, 2021, 405: 126962

[21] Fan J, Du H, Zhao Y. . Recent progress on rational design of bimetallic Pd based catalysts and their advanced catalysis. ACS Catalysis, 2020, 10(22): 13560–13583

[22] Chen X, Zhu H, Zhu J. . Indium-based bimetallic clusters anchored onto silicon-doped graphene as efficient multifunctional electrocatalysts for ORR, OER, and HER. Chemical Engineering Journal, 2023, 451(4): 138998

[23] Zhang J, Wang M, Wan T. . Novel (Pt-O_x)-(Co-O_y) nonbonding active structures on defective carbon from oxygen-rich coal tar pitch for efficient HER and ORR. Advanced Materials, 2022, 34(45): 2206960

[24] Zhang X, Meng H, Chen H. . Bimetallic PtCo alloyed nanodendritic assemblies as an advanced efficient and robust electrocatalyst for highly efficient hydrogen evolution and oxygen reduction. Journal of Alloys and Compounds, 2019, 786: 232–239

[25] Yu W, Zhang Y, Qin Y. . High-density frustrated Lewis pair for high-performance hydrogen evolution. Advanced Energy Materials, 2023, 13(2): 2203136

[26] Fu Z, Wang N, Legut D. . Rational design of flexible two-dimensional MXenes with multiple functionalities. Chemical Reviews, 2019, 119(23): 11980–12031

[27] Peng W, Luo M, Xu X. . Spontaneous atomicruthenium doping in Mo₂CT_x MXene defects enhances electrocatalytic activity for the nitrogen reduction reaction. Advanced Energy Materials, 2020, 10(25): 2001364

[28] Liu H, Dong B. Recent advances and prospects of MXene-based materials for electrocatalysis and energy storage. Materials Today Physics, 2021, 20: 100469

[29] Wang H, Lee J. Recent advances in structural engineering of MXene electrocatalysts. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2020, 8(21): 10604–10624

[30] Tang Y, Yang C, Xu X. . MXene nanoarchitectonics: Defect-engineered 2D MXenes towards enhanced electrochemical water splitting. Advanced Energy Materials, 2022, 12(12): 2103867

[31] Wu Y, Wei W, Yu R. . Anchoring sub-nanometer Pt clusters on crumpled paper-like MXene enables high hydrogen evolution mass activity. Advanced Functional Materials, 2022, 32(17): 2110910

[32] Wang L, Song L, Yang Z. . Electronic modulation of metal-organic frameworks by interfacial bridging for efficient pH-universal hydrogen evolution. Advanced Functional Materials, 2023, 33(1): 2210322

[33] Wang J, Liu Y, Yang Y. . A weldable MXene film assisted by water. Matter, 2022, 5(3): 1042–1055

[34] Hongzhiwei Technology, Device Studio, Version 2023A, China, 2023-5-8, available at the website of HZWTECH

[35] Kresse G, Furthmüller J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Physical Review B: Condensed Matter, 1996, 54(16): 11169–11186

[36] Blöchl P E. Projector augmented-wave method. Physical Review B: Condensed Matter, 1994, 50(24): 17953–17979

[37] Perdew J, Burke K, Ernzerhof M. Generalized gradient approximation made simple. Physical Review Letters, 1996, 77(18): 3865–3868

[38] Li J, Hou C, Chen C. . Collaborative interface optimization strategy guided ultrafine RuCo and MXene heterostructure electrocatalysts for efficient overall water splitting. ACS Nano, 2023, 17(11): 10947–10957

[39] Ding L, Wei Y, Li L. . MXene molecular sieving membranes for highly efficient gas separation. Nature Communications, 2018, 9(1): 155

[40] Ke D, Wang J, Zhang H. . Fabrication of Pt−Co NPs supported on nanoporous graphene as high-efficient catalyst for hydrolytic dehydrogenation of ammonia borane. International Journal of Hydrogen Energy, 2017, 42(43): 26617–26625

[41] Fu F, Wang C, Wang Q. . Highly selective and sharp volcano-type synergistic Ni₂Pt@ZIF-8-catalyzed hydrogen evolution from ammonia borane hydrolysis. Journal of the American Chemical Society, 2018, 140(31): 10034–10042

[42] Meng Y, Sun Q, Zhang T. . Cobalt-promoted noble-metal catalysts for efficient hydrogen generation from ammonia borane hydrolysis. Journal of the American Chemical Society, 2023, 145(9): 5486–5495

[43] Kuang P, Ni Z, Zhu B. . Modulating the d-band center enables ultrafine Pt₃Fe alloy nanoparticles for pH-universal hydrogen evolution reaction. Advanced Materials, 2023, 35(41): 2303030

[44] Wang Y, Chen L, Yu X. . Superb alkaline hydrogen evolution and simultaneous electricity generation by Pt-decorated Ni₃N nanosheets. Advanced Energy Materials, 2017, 7(2): 1601390

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