Review on Magnetism in Catalysis: From Theory to PEMFC Applications of 3d Metal Pt-Based Alloys

Abstract

The relationship between magnetism and catalysis has been an important topic since the mid-20th century. At present time, the scientific community is well aware that a full comprehension of this relationship is required to face modern challenges, such as the need for clean energy technology. The successful use of (para-)magnetic materials has already been corroborated in catalytic processes, such as hydrogenation, Fenton reaction and ammonia synthesis. These catalysts typically contain transition metals from the first to the third row and are affected by the presence of an external magnetic field. Nowadays, it appears that the most promising approach to reach the goal of a more sustainable future is via ferromagnetic conducting catalysts containing open-shell metals (i.e., Fe, Co and Ni) with extra stabilization coming from the presence of an external magnetic field. However, understanding how intrinsic and extrinsic magnetic features are related to catalysis is still a complex task, especially when catalytic performances are improved by these magnetic phenomena. In the present review, we introduce the relationship between magnetism and catalysis and outline its importance in the production of clean energy, by describing the representative case of 3d metal Pt-based alloys, which are extensively investigated and exploited in PEM fuel cells.

How advances in theoretical chemistry meet industrial expectations in electrocatalysts for water splitting

“…, in ammonia synthesis, 136 the Fischer–Tropsch process, 137 and fuel cells. 50 Fig. 7 shows the improved OER current density of Ni foams with deposited RuO 2 nanoparticles.…”

“…The nature of QSEI in magnetic bonds, stable but less bonding, can also relate to the Sabatier principle: the concept of magnetic nobility. 50–53 The non-covalent stabilisation due to inter-atomic QSEI between atoms with open-shell configurations leads to the decrease of: a) the interatomic electronic repulsions within the catalyst itself, and b) the bond strength of the oxygenated reactants and lowering of the activation barriers.…”

“…Industry demands a step forward in the rational design 80 of catalytic electrodes and to realise this, the magnetic properties of the whole catalytic interphase must also be considered at the development stage. 6,10,45,[81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96] MagnetoCat's R&D department is currently pushing fundamental computational chemistry towards the proper inclusion of quantum correlations [4][5][6]50 in the description of complete reaction pathways, materials properties and comprehensive physical models. This methodology allows a common treatment and a fair comparison (with similar accuracy) between closed-shell (weakly correlated) and open-shell catalysts alike.…”

“…The understanding of interactions between electrons in heterogeneous catalysts has substantially improved in the last few years coinciding with a better interpretation of quantum correlations. 4,50–53 We have been able to establish a link between non-linear alterations in catalytic activity, the orbital filling, and the magnetic/spin ordering of materials. 5,51,53 All these scientific advances, which demonstrate the significant influence of (cooperative) electronic correlations on the activity and stability of catalysts, triggered mainly by quantum spin exchange interactions (QSEI), 4 are the spark that may influence the situation for industrial electrocatalysts.…”

Insights into Heterogeneous Catalysis on Surfaces with 3d Transition Metals: Spin-Dependent Chemisorption Models and Magnetic Field Effects

“…However, for the transition metal oxide catalysts usually used in OER and ORR, one may need to consider the effect of the strong electron correlation . For example, recent works by Gracia et al discuss that strongly correlated electrons play a crucial role in the energy of magnetic materials and thus in catalysis. − While catalysis involves a local picture of atoms forming bonds on the surface with one or a few atoms, the electronic structure of the surface can be strongly influenced by the presence of unpaired electrons and their interactions. Gracia et al propose that these interactions can lead to cooperative quantum spin exchange interactions (QSEIs) and quantum excitation interactions (QEXIs), which can affect the efficiency, cost, implementation, and environmental footprint of any heterogeneous catalyst .…”