Synergistic integration of atomic-scale Ni-N sites and Ni nanoparticles for enhanced protonation in pH-universal electrochemical CO2 reduction

Abstract

The development of efficient and stable electrocatalysts for CO₂ reduction is crucial for sustainable CO production. This study introduces a catalyst where Ni nanoparticles and isolated Ni-N sites are supported on mesoporous nitrogen-doped carbon nanotubes (Ni@N-CNTs), which demonstrates exceptional performance in pH-universal environments. The Ni@N-CNTs catalyst achieves a remarkable CO Faradaic efficiency (FE) of about 95% at a current density of 1,200 mA cm⁻² in neutral and alkaline flow cells. Notably, it also maintains high FE (>90%) at current densities ranging from 100 to 900 mA cm⁻² in acidic environments. Furthermore, in membrane electrode assembly (MEA), it achieves over 90% CO FE at 700 mA cm⁻² with prolonged stability. The catalyst can continuously produce CO with 97.5% purity in a practical setting, highlighting its potential for industrial applications. Mechanism studies indicate that the unique interaction between Ni-N and Ni nanoparticles in the Ni@N-CNTs catalyst optimizes the protonation step, enhancing CO formation.