Unraveling the single-atom electrocatalytic activity of transition metal-doped phosphorene

Nair, Akhil S.; Ahuja, Rajeev; Pathak, Biswarup

doi:10.1039/d0na00209g

Cited by 24 publications

(27 citation statements)

References 57 publications

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“…The current densities of each system for HER process have been calculated using the following equation as proposed by Norskov et al where G *H is the free energy of the H* adsorption, T is the temperature, k B is the Boltzmann constant, and k 0 is the rate constant, which has been set to 1 because of the inaccessibility of experimental results in earlier studies for HER activity. 66,67 We also observed that the first hydrogen (*H) adsorbed at the 3-fold hollow site is thermodynamically downhill by −0.69 eV, which corresponds to the H-coverage of 0.25 ML on the Fe-NC as well as periodic surface, as it is observed in Figure S11a, b. In addition, the adsorption of the second (0.5 ML), third (0.75 ML), and fourth (1 ML) *H is further downhill thermodynamically in both cases, as other active three-fold hollow sites are also available, whereas desorbing of H 2 is always an uphill process (Figure S11).…”

Section: Resultsmentioning

confidence: 99%

“…Moreover, a plot with exchange current density vs the Gibbs free energy of adsorption is also given in Figure b, as Δ G *H is the only activity descriptor involved in HER process. The current densities of each system for HER process have been calculated using the following equation as proposed by Norskov et al where G *H is the free energy of the H* adsorption, T is the temperature, k B is the Boltzmann constant, and k 0 is the rate constant, which has been set to 1 because of the inaccessibility of experimental results in earlier studies for HER activity. , …”

Section: Resultsmentioning

confidence: 99%

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Current Density Calculations of an Octahedral Fe Nanocluster for Selective Electrocatalytic for Nitrogen Reduction

Das

Nair

Mandal

et al. 2021

ACS Appl. Nano Mater.

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In this work, an octahedral-shaped iron nanocluster (NC) electrocatalyst has been modeled to examine the pathways of electrochemical nitrogen reduction reaction (NRR) and analyze the catalytic activity over the (110) surface. The Heyrovsky-type associative and dissociative NRR mechanisms on the (110) facet and edge of the NC are systematically elucidated by calculating reaction free energies for all the possible elementary reaction steps in NRR. Our results show that the most of the NRR intermediates (*N 2 , *N 2 H, *N 2 H 2 , *N, *NH, *NH 2 , and *NH 3 ) bind weakly on different sites of the NC in comparison to that on the periodic Fe(110) surface. Importantly, the reaction free energy change for the potential determining step (PDS) in the distal associative mechanism with the formation of *NNH on the NC facet is lower than the edge of NC and periodic Fe(110) surface. Our study also indicates that the PDS (*NH 2 formation) associated with the periodic Fe(110) surface is no longer the same as the reaction is catalyzed by the NC. The calculated value of working potential is observed lower for Fe 85 NC in comparison to that of the periodic Fe(110) surface. Furthermore, the current density plot indicates that the NC shows less hydrogen evolution reaction (HER) activity compared to other considered Fe based systems. Apart from the working potential study, the positive shift of dissolution potential has also been considered for dissolution behavior of Fe from the NC with respect to surface, confirming its stability in an electrochemical environment. The Fe 85 NC electrocatalyst possess quite a low overpotential of 0.29 V for NRR with reduced HER activity, which is further lower compared to that of the well-established Re(111) and enhanced stability toward Fe dissolution in comparison to that of the periodic Fe(110) surface. Therefore, such an NC system may perform as an efficient catalyst for an electrochemical NRR.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Current Density Calculations of an Octahedral Fe Nanocluster for Selective Electrocatalytic for Nitrogen Reduction

Das

Nair

Mandal

et al. 2021

ACS Appl. Nano Mater.

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“…71,72 The scaling relations are generally studied over a set of catalyst surfaces where the reported standard relations are ∆GO=∆GOH+2 for O vs. OH and ∆GOOH=∆GOH+3.2 for OH vs. OOH intermediates (∆G denoting adsorption free energy). 73 Here, we attempt to check the plausibility of such a scaling relationship across different DFT methods for the Pt (111) surface. Previously, Norskov and co-workers have reported the sustainability of OH vs. OOH scaling relation across different functionals despite the systematic error, which was canceled by the inclusion of van der Waal's corrections.…”

Section: Orr Activity Analysismentioning

confidence: 99%

Accounting for Dispersion Effects in DFT Framework of Electrocatalysis: A Case Study of Solvent Mediated Oxygen Reduction Reaction

Nair

Pathak

2021

Preprint

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Density functional theory (DFT) is a pivotal tool in the field of computational electrocatalysis. Dispersion effects, which are not incorporated in the regular DFT framework, play a significant role in improving the accuracy of DFT-based catalytic simulations. We perform a calibration study for addressing the effect of different dispersion corrected DFT methods in determining the electrocatalytic properties by conducting a case study of oxygen reduction reaction (ORR). The distinct trends of these methods towards determining the structural, energetic, and electronic properties of catalysis are scrutinized. By systematically incorporating an upgraded solvation model, the importance of the inclusion of dispersion effects for the accurate prediction of chemical and physical properties governing the catalytic activity is illustrated. The combined thermodynamic and kinetic analysis predicts a uniform ORR activity trend, with semi-empirical dispersion corrected DFT methods emerging as optimal choices with comparable or higher accuracy than advanced van der Waal's methods.

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“…Coming back to Nørskov’s model, the exchange current i for H 2 evolution, a measure of the efficiency of the reaction, is plotted against the H atom adsorption free energy, Δ G H . This model, originally developed for H 2 evolution from extended metal surfaces, is commonly employed in its original formulation also for the study of SACs. − The basic assumption of this model is that the adsorption free energy of the H atom is the only parameter required, as the recombination of two H atoms on the active site gives rise to the formation and desorption of H 2 into the gas phase. This hypothesis is widely verified, and in fact on metal surfaces H 2 can exist only in dissociated form or in a physisorbed state where the molecule is weakly bound to the surface by van der Waals forces .…”

Section: Introductionmentioning

confidence: 99%

Role of Dihydride and Dihydrogen Complexes in Hydrogen Evolution Reaction on Single-Atom Catalysts

2021

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The hydrogen evolution reaction (HER) has a key role in electrochemical water splitting. Recently a lot of attention has been dedicated to HER from single atom catalysts (SACs). The activity of SACs in HER is usually rationalized or predicted using the original model proposed by Nørskov where the free energy of a H atom adsorbed on an extended metal surface M (formation of an MH intermediate) is used to explain the trends in the exchange current for HER. However, SACs differ substantially from metal surfaces and can be considered analogues of coordination compounds. In coordination chemistry, at variance with metal surfaces, stable dihydride or dihydrogen complexes (HMH) can form. We show that the same can occur on SACs and that the formation of stable HMH intermediates, in addition to the MH one, may change the kinetics of the process. Extending the original kinetic model to the case of two intermediates (MH and HMH), one obtains a three-dimensional volcano plot for the HER on SACs. DFT numerical simulations on 55 models demonstrate that the new kinetic model may lead to completely different conclusions about the activity of SACs in HER. The results are validated against selected experimental cases. The work provides an example of the important analogies between the chemistry of SACs and that of coordination compounds.

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Unraveling the single-atom electrocatalytic activity of transition metal-doped phosphorene

Cited by 24 publications

References 57 publications

Current Density Calculations of an Octahedral Fe Nanocluster for Selective Electrocatalytic for Nitrogen Reduction

Current Density Calculations of an Octahedral Fe Nanocluster for Selective Electrocatalytic for Nitrogen Reduction

Accounting for Dispersion Effects in DFT Framework of Electrocatalysis: A Case Study of Solvent Mediated Oxygen Reduction Reaction

Role of Dihydride and Dihydrogen Complexes in Hydrogen Evolution Reaction on Single-Atom Catalysts

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