A first-principles study of 2D Ni–Fe double metal cyanides for CO electroreduction

Abstract

The development of highly efficient catalysts for CO electrocatalytic reduction (COER), a pivotal process in achieving carbon neutrality, remains a formidable challenge. In this study, first-principles density functional theory (DFT) calculations are employed to investigate the catalytic potential of FeNi(CN)₄, a two-dimensional double metal cyanide (2D DMC) featuring Fe–CN–Ni and Fe–NC–Ni isostructures. The electronic and magnetic properties of these isostructures were analyzed using the DFT+U approach, with U parameters determined via the linear response method. A comprehensive exploration of the COER mechanism identified a consistent optimal reaction pathway and rate-determining step across different active sites within the isostructures. Notably, the Fe–NC–Ni (Fe) site demonstrated superior selectivity, favoring CH₃OH production over CH₄ while effectively suppressing the competing hydrogen evolution reaction (HER). This enhanced selectivity is attributed to site-specific electronic properties that govern intermediate adsorption and reaction energetics. Furthermore, the adsorption energy difference between *CO and *CHO species emerged as a reliable activity descriptor, providing a predictive metric for evaluating COER performance on FeNi(CN)₄ monolayers. By establishing a thermodynamic framework for identifying optimal reaction pathways, this study not only advances the understanding of COER mechanisms but also positions two-dimensional Prussian blue analogues, exemplified by FeNi(CN)₄, as promising platforms for the rational design of highly efficient COER electrocatalysts.