Hollow Mesoporous Carbon Sphere Loaded Ni–N₄ Single‐Atom: Support Structure Study for CO₂ Electrocatalytic Reduction Catalyst

Abstract

Single‐atom catalysts have become a hot spot because of the high atom utilization efficiency and excellent activity. However, the effect of the support structure in the single‐atom catalyst is often unnoticed in the catalytic process. Herein, a series of carbon spheres supported Ni–N4 single‐atom catalysts with different support structures are successfully synthesized by the fine adjustment of synthetic conditions. The hollow mesoporous carbon spheres supported Ni–N4 catalyst (Ni/HMCS‐3‐800) exhibits superior catalytic activity toward the electrocatalytic CO2 reduction reaction (CO2RR). The Faradaic efficiency toward CO is high to 95% at the potential range from −0.7 to −1.1 V versus reversible hydrogen electrode and the turnover frequency value is high up to 15 608 h−1. More importantly, the effect of the geometrical structures of carbon support on the CO2RR performance is studied intensively. The shell thickness and compactness of carbon spheres regulate the chemical environment of the doped‐N species in the carbon skeleton effectively and promote CO2 molecule activation. Additionally, the optimized mesopore size is beneficial to improve diffusion and overflow of the substance, which enhances the CO2 adsorption capacity greatly. This work provides a new consideration for promoting the catalytic performance of single‐atom catalysts.

From CO2 to Value-Added Products: A Review about Carbon-Based Materials for Electro-Chemical CO2 Conversion

“…Recent research [139][140][141] highlights two important points to consider when designing single atoms catalysts, as they have been overlooked so far: (1) The first point is that in addition to taking into consideration the formation of catalytic sites, it is crucial to also study the structural geometry of the carbon matrix because it also plays a key role in the catalytic activity since the structure can influence the coordination environment of the single atoms [118,142,143]. Hollow N-doped carbon spheres are a type of support in which individual atoms can be immobilized and their synthesis process allows good control in the design of the catalyst structure.…”

“…For this, templates such as tetraethyl orthosilicate (TEOS) are used, which hydrolyze or condense leaving hollow pores [144]. Several authors [139,[145][146][147][148] synthesized these materials to apply them in the CO 2 electroreduction to CO, however it was not until recently that Xiong and co-workers [139] studied the effect that different geometric structures have on carbon spheres that were used as supports for Ni-N 4 sites. The parameters studied were the shell thickness, compaction, and mesoporous size.…”

Hollow microstructural regulation of single-atom catalysts for optimized electrocatalytic performance

“…Zhang et al [113] constructed a single-shell hollow N-doped carbon matrix (HCM) by the SiO 2 template method to anchor isolated Ni atoms. The isolated Ni atoms coordinate with the surrounding N atoms and the synergistic effect of Ni-N coordination can reduce E F and the adsorption energy of intermediates, which is essential for promoting the OER kinetics in alkaline conditions [113] .…”

Single‐Atom Catalysts: A Sustainable Pathway for the Advanced Catalytic Applications

“…[ 6,7 ] Catalytic activity and selectivity are enabled via the many factors such as accessibility of active sites, interaction with the surface, i.e., varying support and coordinating sphere, composition of metals (bimetallic and many‐metallic), size and shape; and chemical states of active sites which can to tailored via developing 2D catalyst [ 8–10 ] or via developing single atomic sites stabilized on hollow surfaces. [ 11,12 ] For example, Somorjai and co‐workers controlled the selectivity of dendrimer‐encapsulated Au nanoclusters (Au‐G4OH/SBA‐15) by varying the dendrimer properties which is in a similar strategy used by ligand modification in a homogeneous catalyst. [ 13 ] In another example to tune the selectivity, Ag nanowire was found more selective for ethylene epoxidation reaction compared to spherical catalyst.…”