Highly Sensitive, Flexible H₂ Gas Sensors Based on Less Platinum Bimetallic Ni–Pt Nanocatalyst-Functionalized Carbon Nanofibers

Abstract

Flexible electronic gas sensors working at room temperature have acquired enormous attention in recent years due to their suitability to be integrated into various wearable electronic products. In this investigation, we have demonstrated a H 2 gas sensor using less platinum bimetallic nickel−platinum nanocatalyst-functionalized carbon nanofibers (CNFs@Ni−Pt) fabricated on a flexible platform. The flexible CNF@Ni−Pt sensor showed only a negligible decrease in response during mechanical stress under flat (21%) and bent (17%) states after several bending cycles owing to the high aspect ratio of the carbon nanofiber network, which helps us to indulge a long bending path. Moreover, the flexible CNF@Ni−Pt sensor showed superior sensor response (50%) toward H 2 with outstanding selectivity toward other interfering gases. In addition, hydrogen adsorption kinetic studies performed on flexible CNF@Ni−Pt sensors indicated comparable theoretically calculated (0.42) and experimental (0.49) rate constant values. In situ Raman spectroscopy analysis aided in unraveling the H 2 interaction with the catalytically active Ni−Pt sites anchoring on the surface of CNFs, and a plausible sensing mechanism could be predicted. Flexible, less platinum CNF@Ni−Pt sensors can find wider applications in the fields of flexible electronics, biomedical, and environmental monitoring.

Integrated co-axial electrospinning for a single-step production of 1D aligned bimetallic carbon fibers@AuNPs–PtNPs/NiNPs–PtNPs towards H2 detection

“…Overlap of the peaks of Ni and Pt further indicates that the nanoparticles are bimetallic in nature. 21,27,28 A close observation of XRD patterns of co-axial bimetallic systems; CFs@AuNPs-PtNPs and CFs@Ni NPs-Pt NPs reveals that the peak corresponding to (111) plane of Pt has shifted to higher Bragg angles. From Figure 2, it can also be confirmed that there is not any peak matching to fcc Ni or NiO for co-axial CFs@Ni NPs-Pt NPs.…”

“…The lowermost B.E components linked might be ascribed to the zero valent state of metallic platinum NPs. 20,21 The Ni 2p spectrum 40,41 unveiled two weak peaks emerging at 875.2 and 856.41 eV, ascribed to the binding energies of Ni 2p1/2 and Ni 2p3/2 as shown in Figure 6e. Besides, from the XPS spectra it was confirmed that, there were not any further impurity peaks, and the major Pt 4f and Ni 2p peaks confirmed the emergence of Ni NPs-Pt NPs bimetallic NPs on CFs by single-step co-axial electrospinning method.…”

“…In addition, less-PtNPs functionalized carbon support might be more economical and advantageous with improved sensitivity without much shift in the base-resistance. Less-platinum based carbon nanofibers synthesized via two-step method, electrospinning and chemical reduction on flexible substrate for room temperature hydrogen gas detection was discussed in our previous report 21 . Though, incorporation of less-Pt based low-cost bimetallic systems over CFs on flexible substrates improved the sensor characteristics, but, for real-time applications, easy fabrication methods with improved sensor performance are more desirable.…”

“…Figure2shows the X-ray diffraction pattern of pristine CFs, co-axial CFs@PtNPs, co-axial CFs@AuNPs-PtNPs and CFs@Ni NPs-Pt NPs. A wide peak centered at 25.2 was appeared for CFs, co-axial CFs@PtNPs, CFs@AuNPs-PtNPs and CFs@Ni NPs-Pt NPs, which is attributed to the amorphous phase of the graphitic carbon ((002) plane) prevailing in the CFs (JCPDS card 41-1487) 21,23. The XRD pattern of co-axial CFs@PtNPs confirms the existence of the characteristic peaks located at 2 = 39.7, 45.4, 67.9 and 81.2, which were ascribed to the planes (111), (200), (220) and (311) consistent to the fcc platinum (JCPDS card 04-0802), respectively 24.…”

Review of Hydrogen Gas Sensors for Future Hydrogen Mobility Infrastructure

“…Thus, low-power, flexible hydrogen sensors were recently developed using graphene [54], carbon nanotubes [55], and organic/inorganic 2D hybrid materials [56,57]. Among these sensors, carbon crystal structures can detect hydrogen quickly based on their high hydrogen sensitivity but readily react with other gases because of their large surface areas [58]. To overcome this limitation, studies have been conducted to evaluate the effects of doping noble metals such as Pd [54,55].…”