Considerable improvements in the electrocatalytic activity of 2D metal phosphorous trichalcogenides (M₂P₂X₆) have been achieved for water electrolysis, mostly with M^II₂[P₂X₆]⁴⁻ as catalysts for hydrogen evolution reaction (HER). Herein, M^IM^IIIP₂S₆ (M^I = Cu, Ag; M^III = Sc, V, Cr, In) are synthesized and tested for the first time as electrocatalysts in alkaline media, towards oxygen reduction reaction (ORR) and HER. AgScP₂S₆ follows a 4 e⁻ pathway for the ORR at 0.74 V versus reversible hydrogen electrode; CuScP₂S₆ is active for HER, exhibiting an overpotential of 407 mV and a Tafel slope of 90 mV dec⁻¹. Density functional theory models reveal that bulk AgScP₂S₆ and CuScP₂S₆ are both semiconductors with computed bandgaps of 2.42 and 2.23 eV, respectively and overall similar electronic properties. Besides composition, the largest difference in both materials is in their molecular structure, as Ag atoms sit at the midpoint of each layer alongside Sc atoms, while Cu atoms are raised to a similar height to S atoms, in the external segment of the 2D layers. This structural difference probably plays a fundamental role in the different catalytic performances of these materials. These findings show that M^I(Cu, Ag) together with Sc(M^III) leads to promising achievements in M^IM^IIIP₂S₆ materials as electrocatalysts.

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