Molecular Engineering for Bottom-Up Construction of High-Performance Non-Precious-Metal Electrocatalysts with Well-Defined Active Sites

Abstract

In the face of the environmental and energy crisis, the commercialization of advanced electrochemical energy conversion technology based on basic reactions like the hydrogen evolution reaction (HER), the oxygen reduction reaction (ORR), the oxygen evolution reaction (OER), and the CO2 reduction reaction (CO2RR) calls for the development of low-cost and high-efficiency non-precious-metal (NPM) electrocatalysts. The ideal NPM electrocatalysts usually feature (1) highly active intrinsic sites; (2) high-density and uniform active sites to reduce the energy barrier of the reaction and increase the surface electron-mass transfer rate, thus improving the activity, turnover efficiency, and selectivity of the catalyst. Molecular engineering strategy is an effective approach to realize the bottom-up construction of high-performance NPM electrocatalysts with well-defined active sites. In this review, the recent progress about utilizing molecules including small molecules, metal–organic frameworks (MOF), covalent organic frameworks (COF), biomolecules, and polyoxometalate (POM) as precursors to build NPM electrocatalysts (M–NC single-atom catalysts, NPM-based materials, and metal-free carbon-based materials) with high-loading-density and well-defined active sites for electrochemical energy conversion are summarized. Finally, the prospects and challenges for the future development of high-performance and industrially applicable electrocatalysts are proposed.

Rationalizing Structural Hierarchy in the Design of Fuel Cell Electrode and Electrolyte Materials Derived from Metal-Organic Frameworks

“…In addition, those nanostructures that emerge from MOF-derived SACs have excellent active-site support and excellent dispersion properties when applied to electrocatalytic processes. High absorbent properties that persist and are likely better controlled in self-removable supports deliver porous, hollow, structurally defined cavities [51][52][53][54]. According to the results of our study, MOF-designed electrocatalysts for fuel cells are capable of improving their working durability and have the potential to replace precious metals as costly conventional materials.…”

Metal-Free Molecular Catalysts for the Oxygen Reduction Reaction: Electron Affinity as an Activity Descriptor

“…Recently, metal-free heteroatom-doped carbon catalysts have emerged as more efficient, stable, sustainable, inexpensive, and earth-abundant alternatives to conventional Pt-based systems. ,, Among them, graphene-based materials doped with nitrogen, boron, − sulfur, and phosphorus − show remarkable performance. ,,− However, these systems suffer from ambiguity in doping patterns containing multiple heteroatoms, thus obfuscating the identification of active sites. Alternative bottom-up approaches starting from well-defined heteroatom-containing polyaromatic hydrocarbons (PAHs, sometimes termed graphene nanoflakes) address this drawback while potentially preserving the catalytic effect.…”

The Journal of Physical Chemistry C Virtual Special Issue on “Energy and Catalysis in China”

“…The oxygen reduction reaction (ORR) is the most critical electrocatalytic reaction in fuel cells due to its slow kinetics. This VSI includes 7 research papers about the development of efficient or stable ORR catalysts, ultrathin palladium/transition-metal alloy nanowires, Au-modified Pt–Co/C, Pt n Ni tetrahedrons, N , N -di­(2-picolyl)­ethylenediamine (DPEN)-modified Co corrole, Fe–N x –C or Co–N 4 single-atom catalysts, , and Co-, N-, and S-tridoped carbon frameworks for ORR as well as a review paper about non-precious-metal electrocatalysts . Moreover, the influence of the microstructures and transport properties of ionomer films on the performance of Pt single atom catalysts (SACs) in polymer electrolyte membrane fuel cells (PEMFCs) has been reported .…”

“…This VSI includes 7 research papers about the development of efficient or stable ORR catalysts, ultrathin palladium/transition-metal alloy nanowires, 1 Au-modified Pt− Co/C, 2 Pt n Ni tetrahedrons, 3 N , N-di(2-picolyl)ethylenediamine (DPEN)-modified Co corrole, 4 Fe−N x −C or Co−N 4 single-atom catalysts, 5,6 and Co-, N-, and S-tridoped carbon frameworks for ORR 7 as well as a review paper about non-precious-metal electrocatalysts. 8 Moreover, the influence of the microstructures and transport properties of ionomer films on the performance of Pt single atom catalysts (SACs) in polymer electrolyte membrane fuel cells (PEMFCs) has been reported. 9 The development of electrode materials for lithium-ion batteries is included in this VSI: lithium-iron-phosphatecoated LiNi x Co y Mn 1−x−y O 2 (NCM) 10 and porous Co 3 O 4 nanoparticles assembled nanostructures for lithium-ion batteries, 11 and N,S-codoped three-dimensional (3D) network carbon materials supported RuO 2 for Li−O 2 batteries, 12 while Fe-doped PrBa 0.8 Ca 0.2 Co 2 O 6−δ double perovskite oxide is reported as an efficient cathode material for solid oxide fuel cells.…”