Recent Advances in MOF‐Derived Single Atom Catalysts for Electrochemical Applications

Abstract

nanoparticles (NPs) catalysts, SACs display unique features like their unsaturatedcoordination configuration, quantum size effect, and strong atom-support interaction, which induce the single-atom sites with excellent activity and stability in electrocatalysis. [1b,2] In 2011, Zhang and co-workers employed a coprecipitation method to prepare Pt SACs supported on iron oxide which demonstrated high activity and stability for CO oxidation. [3] Sun and co-workers reported the fabrication of Pt SACs on graphene by atomic layer deposition, and the as-prepared Pt SACs showed 10 times higher activity for methanol oxidation and superior CO tolerance compared to the benchmark Pt/C catalyst. [4] According to this research, it can be seen that "single atom catalysts" developed rapidly and have become a hot research topic in heterogeneous electrocatalysis. 1.1. Identification and Features of SACs SACs have isolated metal atoms that are anchored on a specific support and can behave as active centers for heterogeneous catalysis. The concept of single-atom catalysts can be traced back to the pioneering research reported by Zhang and co-workers in 2011. In their work, well-dispersed Pt single atoms were successfully prepared on the FeOx support, which opens the avenue of "single atom catalysts." The active single-atom sites generally consist of metal atoms and neighboring atoms from support materials. In addition, ion-exchanged metal atoms located on a porous support, as well as organometallic complexes anchored to the substrate, in principle, could also be viewed as SACs. The unique features of single atoms are significantly different from NPs, which endow SACs with exceptional catalytic activity, stability and selectivity. i) Decreasing the size of metal particles down to single atoms results in the maximum atom-utilization efficiency and metal dispersion. Owing to the low-coordination environment property and fully exposed active sites, SACs are capable to exhibit remarkable electrocatalytic activity toward diverse reactions. [5] ii) Single metal atoms can coordinate with support materials via strong interaction or charge transfer, which ensure the atomic dispersion and enhanced stability of SACs. [6] iii) The uniform active sites and geometric configuration of SACs enable similar electronic and spatial interactions with reactant molecules, thereby achieving Electrocatalysis plays a critical role in clean energy conversion, enabling great improvement for future sustainable technologies. Single atom catalysts (SACs) derived from metal-organic framework (MOF) are emerging extraordinary materials in electrochemical catalytic applications. Covering the merits of unique electronic structure, low-coordination environment, quantum size effect, and metal-support interaction, SACs promise enhanced electrocatalytic activity, stability, and selectivity in the field of clean energy conversion. In this article, MOF synthesis routes to afford well-dispersed SACs along with the respective synthesis mechanism are systematically reviewed first...

Synthesis Strategies, Catalytic Applications, and Performance Regulation of Single‐Atom Catalysts

“…Hydrogen evolution reaction (HER, the Volmer–Heyrovsky mechanism: H + + e − → H*; H* + H + + e − → H 2 + * or the Volmer–Tafel mechanism H + + e − → H*; 2H* → H 2 + 2*) and oxygen evolution reaction (OER, 2H 2 O → 4e − + 4H + + O 2 at acidic conditions; 4OH − → 2O 2 + 2H 2 O + 4e − at alkaline conditions) are fundamentally important for energy conversion. [ 81,82 ] They occur at the cathode and anode of a water‐splitting electrolyzer, where there is an urgent need to completely replace and/or lower the noble metal catalysts loading, particularly the Pt group metals (e.g., Pt, Pd, Ru, Ir, and Rh) located close to the peak of the volcano curve and demonstrated prominent performance toward HER and OER. [ 83,84 ] Among these reported catalysts, SACs have been regarded as the most efficient one that exposed each atom and have nearly 100% atomic utilization.…”

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

“…[27,28,[64][65][66][67][68][69][70][71][72][73] In this short report, we mainly focused on the applications of SACs in benign ways of energy production (ORR, OER, HER, and metal-air batteries), and organic transformations (with and without electrochemical setup) which are published recently. [74][75][76][77][78] Apart from these applications, electrochemical applications of SA for hydrogen electro-oxidation, [79] formic acid, [80][81][82] methanol, [83,84] and CO oxidation, [85][86][87][88] CO 2 transformation into value-added chemicals which is now a day is a hot arena, [74,89,90] N 2 activation, [91][92][93][94] and metal-sulfur batteries [95][96][97] are highly desirable, but discussion about these topics are out of the scope of this report. These topics will be covered separately in the future review article.…”

Conductive Metal-Organic Frameworks for Electrocatalysis：Achievements, Challenges, and Opportunities

“…Metal-organic frameworks (MOFs), as hybrid crystalline reticular materials composed of organic linkers and metalcontaining nodes, have drawn tremendous attention from researchers because of their captivating and unique advantages like outstanding surface areas, tunable porosity, and framework topologies [1][2][3][4][5] . The combination of these compelling features with well-defined ordered structures makes MOFs promising candidates for a wide variety of applications, such as molecular separations, energy storage and conversion, sensors, magnets, catalysis, biomedicine, and so on [6][7][8][9][10][11][12][13][14][15][16][17] . However, the electronic properties and applications of MOFs have attracted relatively less interest as the majority of MOFs are insulators with inherently weak conductivity (< 10 −10 S•cm −1 ) 18,19 .…”

“…Electrocatalysis has been perceived as one of the cleanest and the most renewable strategies to mitigate environmental issues and energy shortage problems [48][49][50] . More recently, conductive MOFs have been widely investigated as catalysts for electrocatalytic application 10,51 . However, a focused review of the synthesis and electrocatalytic application of conductive MOFs is still lacking.…”