The evaluation of the stability of emerging earth-abundant metal phosphide electrocatalysts by solely electrochemical current-potential sweeps is often not conclusive. In this study, we investigate Co₂P, to evaluate its stability under both acidic (0.5 M H₂SO₄) and alkaline (1.0 M KOH) hydrogen evolution (HER) conditions. We found that the electrochemical surface area of Co₂P only slightly increases in acidic conditions but almost doubled after electrolysis in alkaline electrolyte. The surface composition of the electrode remained almost unchanged in acid but was significantly altered in alkaline during current-potential sweeps. The analysis of the electrolytes after stability test shows almost stoichiometric composition of Co and P in acid but a preferential dissolution of P over Co could be observed in alkaline electrolyte. Applying comprehensive post-catalysis analysis of both electrode and electrolyte, we conclude that Co₂P, prepared by thermal phosphidization, dissolves stoichiometrically in acid and degrades to hydroxides under alkaline stability testing.

Ceria-supported Pd is a promising heterogeneous catalyst for CO oxidation relevant to environmental cleanup reactions. Pd loaded onto a nanorod form of ceria exposing predominantly (111) facets is already active at 50 °C. Here we report a combination of CO-FTIR spectroscopy and theoretical calculations that allows assigning different forms of Pd on the CeO₂(111) surface during reaction conditions. Single Pd atoms stabilized in the form of PdO and PdO₂ in a CO/O₂ atmosphere participate in a catalytic cycle involving very low activation barriers for CO oxidation. The presence of single Pd atoms on the Pd/CeO₂-nanorod, corroborated by aberration-corrected TEM and CO-FTIR spectroscopy, is considered pivotal to its high CO oxidation activity.

Transition metal chalcogenides have been identified as low-cost and efficient electrocatalysts to promote the hydrogen evolution reaction in alkaline media. However, the identification of active sites and the underlying catalytic mechanism remain elusive. In this work, we employ operando X-ray absorption spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy to elucidate that NiS undergoes an in-situ phase transition to an intimately mixed phase of Ni₃S₂ and NiO, generating highly active synergistic dual sites at the Ni₃S₂/NiO interface. The interfacial Ni is the active site for water dissociation and OH* adsorption while the interfacial S acts as the active site for H* adsorption and H₂ evolution. Accordingly, the in-situ formation of Ni₃S₂/NiO interfaces enables NiS electrocatalysts to achieve an overpotential of only 95 ± 8 mV at a current density of 10 mA cm⁻². Our work highlighted that the chemistry of transition metal chalcogenides is highly dynamic, and a careful control of the working conditions may lead to the in-situ formation of catalytic species that boost their catalytic performance.

We present a dual passivation approach for p–i–n perovskite solar cells using phenethylammonium chloride that simultaneously passivates defects at the grain boundaries and the perovskite/C ₆₀ interface, thus substantially enhancing both V _OC and FF.

In this review article, we summarise the key electronic features of transition metal oxides that govern their OER catalytic properties, and how such electronic descriptors are applied for OER electrocatalysts design.