IrNiCu@Cu Nanostructures With hcp Cu Shells for Nitrate Reduction
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Solution Overview
Problem
Conventional electrocatalysts for nitrate reduction (NO3RR) face inadequate catalytic activities and instability under ambient conditions, particularly in preparing unconventional hexagonal close-packed (hcp) copper (Cu) phases, which are crucial for enhancing the electrochemical nitrate reduction reaction (NO3RR) efficiency.
Innovation Solution
A method is developed to manufacture IrNi nanobranches (NBs) and IrNiCu@Cu nanostructures in the hcp phase, involving sequential steps of mixing Ir(acac)3 and Ni(acac)2 with oleylamine and oleic acid, adding formaldehyde, heating, and centrifugation, followed by the addition of Cu(acac)2 to form IrNiCu@Cu nanostructures, which are then used to enhance the NO3RR performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional face-centered cubic (fcc) copper phases are used in electrocatalysts, then the catalysts are stable under ambient conditions, but the catalytic activity for nitrate reduction is insufficient
Solution Approach 1:
The invention changes the crystal phase parameter of copper from conventional fcc to unconventional hcp phase, which fundamentally alters the catalytic properties while maintaining stability. This phase transition enables superior catalytic activity for nitrate reduction to ammonia while preserving ambient stability through controlled synthesis methods
Solution Approach 2:
The invention creates composite nanostructures combining IrNi alloy core with hcp Cu shell (IrNiCu@Cu), where each component contributes its unique properties: IrNi provides structural stability and catalytic sites, while hcp Cu enhances nitrate reduction activity. This composite structure achieves synergistic effects that resolve the stability-activity trade-off
2Productivity
If unconventional hcp copper phase is prepared to enhance NO3RR efficiency, then the catalytic performance is significantly improved, but the preparation process becomes more difficult and complex
Solution Approach 1:
The invention performs preliminary action by first synthesizing IrNi nanobranches with a specific crystal structure that serves as a template, then subsequently growing hcp Cu shells on these pre-formed structures. This sequential approach simplifies the overall process of creating complex hcp Cu structures compared to attempting to synthesize them directly
Solution Approach 2:
The IrNi alloy nanobranches act as an intermediary structure that facilitates the formation of hcp Cu phase. The IrNi core provides a template and controlled environment for Cu deposition, enabling the formation of unstable hcp phase through epitaxial growth, thereby simplifying the preparation process
3Productivity
If the copper shell thickness is increased to improve catalytic activity, then the NO3RR performance is enhanced, but the Faradaic efficiency for ammonia production decreases due to side reactions
Solution Approach 1:
The invention applies local quality by creating a thin hcp Cu shell layer (optimally 2-5 nm) that provides sufficient catalytic activity for nitrate reduction while maintaining high Faradaic efficiency for ammonia production. The localized thin shell structure prevents excessive hydrogen evolution side reactions that occur with thicker Cu layers, thus optimizing the balance between activity and selectivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The IrNiCu@Cu nanostructures exhibit superior catalytic performance, achieving high Faradaic efficiency and ammonia yield rates, with IrNiCu@Cu-20 showing an NH3 Faradaic efficiency of 86% and yield rate of 687.3 mmol gCu−1 h−1, significantly outperforming conventional Cu phases, and IrNiCu@Cu-30 and IrNiCu@Cu-50 demonstrating high selectivity towards nitrite (NO2−).
Implementation Method 1
IrNiCu@Cu nanostructures exhibit superior catalytic performance, achieving high Faradaic efficiency and ammonia yield rates
Implementation Method 2
subjecting the first mixture to ultrasonication to obtain a homogenous solution
Implementation Method 3
subjecting the growth solution to heating in a reactor
Implementation Method 4
harvesting the IrNi NB templates by subjecting the growth solution to centrifugation
Implementation Method 5
adding formaldehyde (HCHO) to the homogenous solution to form a second mixture, the second mixture being a growth solution
Data Source
AI summary
The present invention is concerned with the epitaxial growth of unconventional 2H Cu on hexagonal close-packed (hcp) IrNi template, leading to forming of IrNiCu@Cu nanostructures as electrocatalyst. IrNiCu@Cu-20 shows superior catalytic performance, with NH3 Faradaic efficiency (FE) of 86% at −0.1 (vs reversible hydrogen electrode (RHE)) and NH3 yield rate of 687.3 mmol gCu−1 h−1, far better than common face-centered cubic (fcc) Cu. IrNiCu@Cu-30 and IrNiCu@Cu-50 covered by hcp Cu shell display high selectivity towards nitrite (NO2−), with NO2− FE above 60% at 0.1 (vs RHE). IrNiCu@Cu-20 has the optimal electronic structures for NO3RR due to the highest d-band center and strongest reaction trend with the lowest energy barriers. The electrocatalysts are effective in electrochemical nitrate reduction NO3RR.