Abstract
The scarcity and cost of noble metals used in commercial electrolyzers limit the sustainability and scalability of water electrolysis for green hydrogen production. Herein, we report the ultralow loading of Au nanoparticles onto MoS2 electrodes by the spontaneous process of galvanic deposition. AuNP@MoS2 electrode synthesis was optimized, and electrodes containing the smallest Au nanoparticle diameter (2.9 nm) and the lowest Au loading (0.044 μg cm–2) exhibited the best overall and intrinsic electrocatalytic performance. This enhancement is attributed to an increased Au–MoS2 interaction with smaller nanoparticles, making the MoS2 electrode more n-type. DC electrochemical characterization for the AuNP@MoS2 electrodes showed an exchange current density of 7.28 μA cm–2 and an overpotential at 10 mA cm–2 of −323 mV. These values are 4.5 times higher and 100 mV lower than those of the unmodified MoS2 electrode, respectively. Electrochemical AC experiments were used to evaluate the electrodes’ intrinsic catalytic activity, and it was shown that the AuNP@MoS2 electrodes exhibited an enhanced activity by as much as 3.5 times compared with MoS2. Additionally, the turnover frequency as estimated by the reciprocal of the RctCdl product, the latter calculated from the AC data, is estimated to be 58.8 s–1 and is among one of the highest reported for composite MoS2 materials.
Highlights
Calculated from the data, is estimated to be Hydrogen is widely recognized as a key enabler to the complete decarbonization of our energy system.[1−5] For example, the European Union recently identified the need to prioritize the development of “green” hydrogen to enable carbon neutrality by 2050 and limit the amount of global warming to the levels set by the Paris Agreement in 2015.6,7 Electrolysis offers a route to “green” hydrogen, but in 2018, over 99% of hydrogen was still being produced using fossil fuels.[2]
An inert carrier gas was used to ensure MoS2 formation as the same precursor has been used to produce MoO3 at low temperatures from reactive melts when completed under atmospheric conditions.[49]
The aerosol-assisted chemical vapor deposition (AACVD)-grown MoS2 has previously been extensively characterized using Raman, pXRD, and scanning electron microscopy (SEM) with energydispersive X-ray (EDX) spectroscopic mapping.[56]. Both the Raman spectrum and pXRD patterns were consistent with 2H-MoS2 and EDX spectroscopic mapping, which confirmed that the spatial distribution of the elements was consistent with MoS2
Summary
Hydrogen is widely recognized as a key enabler to the complete decarbonization of our energy system.[1−5] For example, the European Union recently identified the need to prioritize the development of “green” hydrogen to enable carbon neutrality by 2050 and limit the amount of global warming to the levels set by the Paris Agreement in 2015.6,7 Electrolysis offers a route to “green” hydrogen, but in 2018, over 99% of hydrogen was still being produced using fossil fuels.[2]. As 1TMoS2 is metastable, resulting in conversion to the 2H-MoS2 in ambient conditions, much work has been directed toward improving the performance of 2H-MoS2. Pt−MoS2 materials have been shown to deliver improved overall catalytic activity when compared with commercial Pt/C catalysts with the same Pt loading.[16,17] it is worth noting at this point that direct comparison of prospective catalysts for the HER requires consideration of both the overall catalytic activity (current density per geometric area) and the intrinsic catalytic activity. It is important to consider the overall catalytic activity from the perspective of applications, electrodes with
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