For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm⁻² at 80 °C with a low platinum loading of 0.09 mg_Pt cm⁻², corresponding to a platinum utilization of 0.13 g_Pt kW⁻¹ in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

The poor stability of Ru-based acidic oxygen evolution (OER) electrocatalysts has greatly hampered their application in polymer electrolyte membrane electrolyzers (PEMWEs). Traditional understanding of performance degradation centered on influence of bias fails in describing the stability trend, calling for deep dive into the essential origin of inactivation. Here we uncover the decisive role of reaction route (including catalytic mechanism and intermediates binding strength) on operational stability of Ru-based catalysts. Using MRuO_x (M = Ce⁴⁺, Sn⁴⁺, Ru⁴⁺, Cr⁴⁺) solid solution as structure model, we find the reaction route, thereby stability, can be customized by controlling the Ru charge. The screened SnRuO_x thus exhibits orders of magnitude lifespan extension. A scalable PEMWE single cell using SnRuO_x anode conveys an ever-smallest degradation rate of 53 μV h⁻¹ during a 1300 h operation at 1 A cm⁻².

Achieving CO₂reduction with H₂O on metal photocatalysts and understanding the corresponding mechanisms at the molecular level are challenging. Herein, we report that quantum-sized Au nanoparticles can photocatalytically reduce CO₂to CO with the help of H₂O by electron-hole pairs mainly originating from interband transitions. Notably, the Au photocatalyst shows a CO production rate of 4.73 mmol g⁻¹h⁻¹(~100% selectivity), ~2.5 times the rate during CO₂reduction with H₂under the same experimental conditions, under low-intensity irradiation at 420 nm. Theoretical and experimental studies reveal that the increased activity is induced by surface Au–O species formed from H₂O decomposition, which synchronously optimizes the rate-determining steps in the CO₂reduction and H₂O oxidation reactions, lowers the energy barriers for the *CO desorption and *OOH formation, and facilitates CO and O₂production. Our findings provide an in-depth mechanistic understanding for designing active metal photocatalysts for efficient CO₂reduction with H₂O.