Catalyst system, electrode and fuel cell or electrolyzer

A catalyst system comprising, an electrically conductive carrier metal oxide having an electrical conductivity λ1 of at least 10 S/cm, the carrier metal oxide having at least two first metallic elements selected from the group of non-precious metals consisting of tin, tantalum, niobium, titanium, hafnium, and zirconium, and having a structure comprising oxide grains with a grain size of at least 30 nm;

• an electrically conductive, metal oxide catalyst material having an electrical conductivity λ2 of at least 10 S/cm, the catalyst material having at least one second metallic element from the group of non-precious metals comprising tantalum, niobium, hafnium, zirconium, iron, tungsten, and molybdenum, the at least two first metallic elements in the carrier metal oxide and the at least one second metallic element in the catalyst material each being present in a solid stoichiometric compound or solid homogeneous solution;
• the carrier metal oxide having a first crystal lattice structure comprising first oxygen lattice sites and first metal lattice sites, the carrier metal oxide on the first oxygen lattice sites being doped with at least one of fluorine and at least one element from the group comprising nitrogen, carbon, or boron;
• the catalyst material having a second crystal lattice structure comprising second oxygen lattice sites and second metal lattice sites, wherein the catalyst material on the second oxygen lattice sites is doped with fluorine and at least one element from the group comprising nitrogen, carbon, or boron;
• and
• the carrier metal oxide and the catalyst material differing in a composition thereof, a near-surface pH, called pzzp value (pzzp=point of zero zeta potential), of the carrier metal oxide and the catalyst material differ, and the catalyst material and the carrier metal oxide at least forming a two-phase disperse oxide composite;
• wherein the carrier metal oxide and the catalyst material differ in a surface energy thereof, wherein a first phase of the at least two-phase disperse oxide composite has a more hydrophobic surface than a further surface of at least one further phase, and the surface energy of the more hydrophobic surface of the first phase is in a range from 22 to 28 Nm/mm2.