Enhancing electrocatalytic activities of high-entropy borides (HEBs) for C–N coupling in induced cation and pH-dependent microenvironments via multiscale modeling strategy

Abstract

Currently, the renewable energy-driven carbon dioxide reduction reaction (CO₂RR) has been identified as a promising carbon neutralization option capable of generating a variety of high-value hydrocarbon products. Importantly, high-entropy borides (HEBs), which are similar to high-entropy carbides, have attracted extensive attention because of their outstanding chemical and physical properties, which allow them to be used as potential electrocatalysts, expanding the applications of high-entropy alloy materials. TiCrMnFeMoB is a new class of HEBs derived from Mo₂B₂ MBenes via boro/carbothermal reduction. The electrochemical reduction of nitrate (NO₃)-integrated CO₂ to organonitrogen compounds (acetamide and urea) via C–N coupling is attracting increasing attention. This paper outlines a development route and strategy in this area, emphasizing the importance of electrochemical NO₃-integrated CO₂RR for achieving a carbon-neutral society. C–N coupling proceeds by the interaction between ketene (*CCO) vs. ammonia (NH₃) or carbon monoxide (*CO) vs. hydroxylamine (NH₂OH) and the K⁺ cation in the acid electrolyte. The *CCO intermediate forms *CC(OH)NH₂ as a result of the nucleophilic attack by NH₃. The K⁺ cation and pH-dependent modulating reaction microenvironments play important roles in the design of high-performance catalysts for C–N bond coupling and C–C bond formation, which is critical for synthesizing valuable C–N chemicals from the CO₂RR-integrated NO₃ reduction reaction (NtrRR). However, this route still faces many challenges in generating crucial intermediates during electrocatalytic C–N coupling. For the first time, we propose a general modeling strategy for K⁺-induced and pH-dependent microenvironment electroreduction of CO₂ and NO₃ to acetamide and urea, respectively, over HEB catalysts under neutral, acidic, and alkaline conditions. Our results identified *CCO and *NH₂OH as the key intermediates for acetamide and urea synthesis, respectively, undergoing a nucleophilic reaction. This suggests that C–N coupling can occur via a nucleophilic reaction between *CCO and NH₃ to further form acetamide, whereas CO and NH₂OH form urea via two C–N coupling steps. This strategy expands the range of products generated from CO₂ reduction and has been successfully applied to the formation of organonitrogen compounds.