A high activity of a two-dimensional (2D) copper oxide (CuO) electrocatalyst for the oxygen evolution reaction (OER) is presented. The CuO electrode self-assembles on a stainless steel substrate via chemical bath deposition at 80 °C in a mixed solution of CuSO₄ and NH₄OH, followed by air annealing treatment, and shows a 2D nanosheet bundle-type morphology. The OER performance is studied in a 1 M KOH solution. The OER starts to occur at about 1.48 V versus the RHE (η = 250 mV) with a Tafel slope of 59 mV dec⁻¹ in a 1 M KOH solution. The overpotential (η) of 350 mV at 10 mA cm⁻² is among the lowest compared with other copper-based materials. The catalyst can deliver a stable current density of >10 mA cm⁻² for more than 10 hours. This superior OER activity is due to its adequately exposed OER-favorable 2D morphology and the optimized electronic properties resulting from the thermal treatment.

L-Ti₃C₂ was prepared by exfoliating Ti₃AlC₂ in 40% HF. With sulfur-loaded L-Ti₃C₂ as cathodes, Li–S batteries deliver a high initial discharge capacity of 1291 mA h g⁻¹, an excellent capacity retention of 970 mA h g⁻¹ and coulombic efficiency of 99% after 100 cycles.

Surface passivation in perovskite solar cells can enhance device efficiency, yet incomplete interfacial functionality poses challenges to long-term reliability. Here we present a strategic interfacial engineering approach using sodium heptafluorobutyrate to fully functionalize the perovskite surface. Sodium heptafluorobutyrate acts as an ion shield that tunes the perovskite surface work function and increases the defect formation energy, resulting in an improved interface with the electron transport layer that minimizes recombination and boosts electron extraction under operation. We find that a sodium-heptafluorobutyrate-functionalized perovskite surface promotes a uniform, compact C ₆₀ layer that effectively blocks ion diffusion and stabilizes the device stack. This approach allows p–i–n perovskite solar cells to achieve a record power conversion efficiency (PCE) of 27.02% (certified 26.96% with a maximum-power-point-tracking PCE of 26.61%). Devices with an active area of 1 cm ² deliver a PCE of 25.95%. Perovskite solar cells retain 100% of their initial efficiency following 1,200 h of continuous 1-sun illumination at the maximum power point. Devices also demonstrate exceptional thermal stability, retaining 92% of the initial PCE when ageing at 85 °C for 1,800 h and 94% after 200 thermal cycles between –40 °C and +85 °C.