Highly Efficient Electrocatalyst for Oxygen Evolution Reaction: DFT Investigation on Transition Metal‐Tetracyanoquinodimethane Monolayer

Abstract

To search for efficient electrocatalyst towards oxygen evolution reaction (OER) for sustainable energy production, a family of transition metal-tetracyanoquinodimethane (TM-TCNQ) (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd)monolayers have been studied by first principle based density functional theory (DFT) computations. The systematic investigations on various TM-TCNQ structures revealed that Ni-TCNQ monolayer exhibits best catalytic activity towards OER. At equilibrium potential (1.23 Vvs RHE), the free energy profile of Ni-TCNQ monolayer for different reaction intermediates is not completely downhill which points out that water could not be oxidized by the photo-generated holes at that potential. However, at and above 1.71 V, all the OER reaction steps on Ni-TCNQ surface is found to be thermodynamically downhill, measuring a low onset overpotential, ca. 0.48 V in acidic media (pH = 0). The estimated overpotential for other TM-TCNQ structures are comparatively higher to promote energy-efficient OER activity. The excellent performance of Ni-TCNQ monolayer as OER catalyst were explained in terms of volcano plot, scaling diagram, d-band centre model, band structure and charge analysis.

Insights from density functional theory calculations on heteroatom P-doped ZnIn2S4 bilayer nanosheets with atomic-level charge steering for photocatalytic water splitting

“…( 4 ) and ( 5 ) respectively) presented an uphill process in the absence of an applied bias U. Similar to pristine ZIS, OER4 was observed to be the RDS at the standard equilibrium potential for OER (U = 1.23 V) with a value of 5.123 V. It is noteworthy that even though P-doping reduced the overpotential by 0.024 V and out-performed pristine ZIS in the OER intermediate steps, the high (> 1 V) indicated that P-ZIS was not energetically efficient in promoting OER for O 2 production via overall water splitting 56 . Owing to the infeasibility of OER4’s uphill process, the HOO* radical is anticipated to undergo oxidative recombination with H + to produce H 2 O 2 instead 59 , 60 .…”

“…In short, OER consists of 4 elementary reaction steps (OER1, OER2, OER3 and OER4) as listed in Eqs. ( 2 – 5 ) 43 , 56 : where * represents the surface active site, and X* denotes an adsorbed intermediate (X) on the surface active site. The Gibbs free energy for each OER reaction step (∆G OER ) was evaluated based on the corresponding E f of each component and correction factors based on DFT computation 43 , 56 – 58 (see Supplementary Information online for calculation details).…”

“…( 2 – 5 ) 43 , 56 : where * represents the surface active site, and X* denotes an adsorbed intermediate (X) on the surface active site. The Gibbs free energy for each OER reaction step (∆G OER ) was evaluated based on the corresponding E f of each component and correction factors based on DFT computation 43 , 56 – 58 (see Supplementary Information online for calculation details). For comparison, the overpotential required to achieve a downhill trend for all OER free-energy steps at standard equilibrium potential (where external bias U = 1.23 V 56 ) was evaluated using Eq.…”

Exploration of cobalt(ii) modification in a phenanthroline-based conjugated organic polymer towards trifunctional electrocatalysis

“…Interestingly, the overpotential was reduced greatly in Co@TBB-phen in comparison with TBB-phen, thereby signifying the role of cobalt in COPs. 79 Due to the unfilled d-orbitals of cobalt, it acts as a center of the electrophilic attack, and, with sufficient delocalization, the OER proceeds at lower overpotentials, which was challenging to achieve in metal-free TBB-phen. DFT computations were also performed to obtain a fundamental understanding of the HER process.…”