Porosity Engineering Within Ni─N─C Hollow Spheres for Ampere-Level CO₂ Reduction Electrocatalysis

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• CO2 electroreduction often requires high overpotentials, leading to competing hydrogen evolution reactions (HER).
• Achieving high product selectivity (>95%) at high current densities (approaching 1 A cm-2) remains a significant challenge.

Purpose of the Study:

• To synthesize and optimize hollow Ni-NC (H-Ni-NC) electrocatalysts for efficient CO2 electroreduction.
• To investigate the role of nanoscale porosity in catalyst performance.

Main Methods:

• Synthesis of H-Ni-NC using silica sphere templates and atomic Zn as a sacrificial pore-former.
• Electrochemical testing in a flow cell to evaluate performance at high current densities.
• Finite-element simulations to model porosity effects.

Main Results:

• The optimized H-Ni-NC achieved a current density of -1.0 A cm-2 with over 95% CO Faradaic efficiency.
• Zn dosage was found to modulate shell through-porosity without altering catalyst structure.
• Simulations suggested a trade-off between reactant transport and active surface area with increasing porosity.

Conclusions:

• Hollow sphere architecture with gas-permeable through-pores enhances electrocatalyst performance.
• Engineering the nanoscale mass-transport environment is crucial for designing high-efficiency electrocatalysts.
• This study provides a systematic approach to understanding and optimizing catalyst porosity for CO2 electroreduction.