The Construction of Surface-Frustrated Lewis Pair Sites to Improve the Nitrogen Reduction Catalytic Activity of In2O3

At a Glance

Metadata	Details
Publication Date	2023-10-17
Journal	Molecules
Authors	Mingqian Wang, Ming Zheng, Yuchen Sima, Chade Lv, Xin Zhou
Institutions	Harbin Institute of Technology, Heilongjiang Institute of Technology
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Electrocatalysis for Nitrogen Reduction

This document analyzes the research on Surface-Frustrated Lewis Pair (SFLP) sites for Nitrogen Reduction Reaction (NRR) catalysis and connects the material requirements to 6CCVD’s advanced MPCVD diamond capabilities, specifically focusing on Boron-Doped Diamond (BDD) as a superior electrochemical platform.

Executive Summary

Core Achievement: Researchers successfully designed and modeled stable Surface-Frustrated Lewis Pair (SFLP) sites on the Indium Oxide (In₂O₃) (110) surface via heteroatom doping to enhance electrocatalytic Nitrogen Reduction Reaction (NRR).
Optimal Catalyst: Density Functional Theory (DFT) and Ab initio Molecular Dynamics (AIMD) simulations identified P-doped In₂O₃ (P@In₂O₃) as the most stable and efficient catalyst among eight candidates (C, N, F, Si, P, S, Cl).
High Selectivity: P@In₂O₃ demonstrated excellent catalytic selectivity for NRR, effectively suppressing the competing Hydrogen Evolution Reaction (HER), a critical challenge in aqueous electrocatalysis.
Low Limiting Potential: The limiting potential (U_L) for NRR on P@In₂O₃ was calculated at a highly favorable -0.28 eV, indicating low energy input requirements for ammonia synthesis.
Mechanism Elucidation: The catalytic activity relies on a unique “donation-acceptance” mechanism where the electron-rich P atom acts as a Lewis base and the In atom acts as a Lewis acid, synergistically activating the inert N≡N triple bond.
Methodology: The study relied heavily on advanced computational methods (DFT, AIMD at 400 K, Gibbs Free Energy calculations) to screen and validate catalyst stability and performance.

Technical Specifications

Parameter	Value	Unit	Context
Limiting Potential (U_L)	-0.28	eV	P@In₂O₃ NRR (Enzymatic Mechanism PDS)
Limiting Potential (U_L)	-0.285	eV	P@In₂O₃ NRR (Distal Mechanism PDS)
N₂ Adsorption Energy (P@In₂O₃)	-0.10	eV	Stable N₂ adsorption
N₂ Adsorption Energy (S@In₂O₃)	-0.46	eV	Strongest N₂ adsorption observed
Adsorbed N-N Bond Length (P@In₂O₃)	1.17	Å	Activated N-N bond (vs. 1.108 Å free N₂)
Gibbs Free Energy (ΔG)	0.19	eV	First hydrogenation (N₂* → N₂H*) on P@In₂O₃
AIMD Simulation Temperature	400	K	Stability testing of doped structures
AIMD Simulation Time	10	ps	Total simulation duration
Dielectric Constant	78.5	N/A	Simulating aqueous environment (Implicit Solvent Model)
Kinetic Energy Cutoff	630	eV	DFT calculation parameter
Force Convergence Criterion	< 0.03	eV Å^-1	Geometry optimization criterion

Key Methodologies

The research utilized high-level computational modeling to predict and validate the performance of the proposed electrocatalysts:

Computational Framework: Density Functional Theory (DFT) calculations were performed using the DS-PAW and VASP packages, employing the Projection-Augmented Wave (PAW) base set.
Exchange-Correlation Function: The Perdew, Burke, and Ernzerhof (PBE) Generalized Gradient Approximation (GGA) was used, incorporating the Grimme D3 correction to accurately model van der Waals (vdW) interactions.
Surface Modeling: The thermodynamically stable body-centered cubic bixbyite (c-In₂O₃) (110) surface was modeled in a (1 x √2) supercell, fixed with a 15 Å vacuum gap to prevent periodic interactions.
Stability Testing: Ab initio Molecular Dynamics (AIMD) simulations were conducted in a canonical ensemble (NVT) at 400 K for 10 ps to test the thermal stability of the doped SFLPs structures.
Electrochemical Environment: The implicit solvent model was applied to calculate Gibbs free energies, simulating the aqueous environment by setting the dielectric constant to 78.5.
Electronic Structure Analysis: Partial Densities of States (PDOS) and Projected Crystal Orbital Hamilton Population (pCOHP) analyses were used to confirm the electron “donation-acceptance” mechanism and orbital hybridization between the dopant (P) and N₂.

6CCVD Solutions & Capabilities

The research highlights the critical need for highly stable, selective, and conductive electrode materials capable of suppressing HER while facilitating complex surface chemistry (Lewis acid/base sites) for NRR. While this study focused on In₂O₃, Boron-Doped Diamond (BDD) is the industry standard for achieving these exact requirements in demanding electrochemical applications.

6CCVD provides the foundational materials necessary to transition this advanced electrocatalysis research from theoretical modeling to high-performance experimental systems.

Applicable Materials: The BDD Advantage for NRR

The primary challenge in NRR is the competition from HER. BDD electrodes are uniquely suited to overcome this due to their exceptional properties:

Heavy Boron-Doped Diamond (BDD): 6CCVD offers highly conductive BDD (both SCD and PCD) wafers. BDD possesses the widest potential window of any electrode material, effectively shifting the onset potential for HER and maximizing the Faradaic efficiency for NRR, directly addressing the selectivity issues discussed in the paper.
Ultra-High Stability: Unlike metal oxides or carbon-based catalysts, MPCVD BDD exhibits extreme chemical inertness and stability under harsh electrochemical conditions (high current density, wide pH range), ensuring long-term catalyst integrity.

6CCVD Material Recommendation	Key Benefit for NRR Research	Available Specifications
Heavy Boron-Doped PCD Wafers	High conductivity, large area (up to 125mm), and superior HER suppression compared to traditional catalysts.	Plates/wafers up to 125mm diameter. Thicknesses from 0.1µm to 500µm.
Optical Grade SCD	Ideal for fundamental studies requiring ultra-low defect density and atomic-level surface control for precise SFLP replication or modification.	Thicknesses from 0.1µm to 500µm. Polishing: Ra < 1nm.

Customization Potential for Advanced Electrocatalysis

To replicate or extend the complex surface science described in this paper, 6CCVD offers comprehensive customization services:

Custom Dimensions: We provide custom-cut BDD plates and wafers up to 125mm (PCD) or smaller, highly polished SCD, ensuring seamless integration into specialized electrochemical flow cells and reactors.
Precision Polishing: Achieving reproducible surface modification (like the heteroatom doping or vacancy creation discussed) requires an atomically flat starting surface. We guarantee ultra-smooth surfaces: Ra < 1nm (SCD) and Ra < 5nm (Inch-size PCD).
Advanced Metalization: For creating robust, low-resistance ohmic contacts essential for high-current electrocatalysis experiments, 6CCVD offers internal metalization capabilities, including deposition of Au, Pt, Pd, Ti, W, and Cu.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing diamond material properties (boron concentration, surface termination, defect engineering) for high-efficiency electrochemical applications. We can assist researchers in selecting the optimal BDD substrate to maximize NRR selectivity and stability, offering a robust, high-performance platform superior to the complex oxide systems studied here.

Call to Action: For custom specifications or material consultation regarding high-performance BDD electrodes for NRR, HER suppression, or other advanced electrochemical projects, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).

View Original Abstract

The construction of a surface-frustrated Lewis pairs (SFLPs) structure is expected to break the single electronic state restriction of catalytic centers of P-region element materials, due to the existence of acid-base and basic active canters without mutual quenching in the SFLPs system. Herein, we have constructed eight possible SFLPS structures on the In2O3 (110) surface by doping non-metallic elements and investigated their performance as electrocatalytic nitrogen reduction catalysts using density functional theory (DFT) calculations. The results show that P atom doping (P@In2O3) can effectively construct the structure of SFLPs, and the doped P atom and In atom near the vacancy act as Lewis base and acid, respectively. The P@In2O3 catalyst can effectively activate N2 molecules through the enzymatic mechanism with a limiting potential of −0.28 eV and can effectively suppress the hydrogen evolution reaction (HER). Electronic structure analysis also confirmed that the SFLPs site can efficiently capture N2 molecules and activate N≡N bonds through a unique “donation-acceptance” mechanism.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules28207130

References

2018 - A Review of Electrocatalytic Reduction of Dinitrogen to Ammonia under Ambient Conditions [Crossref]
2020 - Rational Catalyst Design for N2 Reduction under Ambient Conditions: Strategies toward Enhanced Conversion Efficiency [Crossref]
2020 - Aqueous electrocatalytic N2 reduction for ambient NH3 synthesis: Recent advances in catalyst development and performance improvement [Crossref]
2019 - Heterogeneous electrocatalysts design for nitrogen reduction reaction under ambient conditions [Crossref]
2023 - Recent progress in electrocatalytic nitrogen reduction to ammonia (NRR) [Crossref]
2021 - Comprehensive Understanding of the Thriving Ambient Electrochemical Nitrogen Reduction Reaction [Crossref]
2021 - Electrochemical reduction of nitrogen to ammonia: Progress, challenges and future outlook [Crossref]
2018 - Nitrogen fixation and reduction at boron [Crossref]
2020 - A Highly Efficient Metal-Free Electrocatalyst of F-Doped Porous Carbon toward N2 Electroreduction [Crossref]
2020 - Boosting Electrocatalytic Ammonia Production through Mimicking “π Back-Donation” [Crossref]