Yu Chen

Reversible protonic ceramic electrochemical cells (R‐PCECs) require air electrodes with fast oxygen reduction/evolution reactions (ORR/OER) and excellent durability under low‐temperature, high‐humidity operating conditions. Herein, we report a rationally designed fluorite catalyst, Pr _0.025 Nd _0.025 La _0.025 Sm _0.025 Ce _0.9 O _x (PNLSC), deposited on a PrBa _0.8 Ca _0.2 Co ₂ O _5+δ (PBCC) backbone for constructing a hybrid air electrode with enhanced electrocatalytic activity and structural durability. Systematic electrochemical investigations, combined with entropy‐dependent comparisons, demonstrate that the designed PNLSC coating can accelerate surface oxygen exchange kinetics, facilitate ionic transport, and suppress surface degradation in humidified atmospheres. In situ infrared spectroscopy analyses directly reveal the optimized surface hydration kinetics and suppressed hydroxyl‐related surface degradation on the PNLSC hybrid electrode, providing mechanistic evidence for its enhanced oxygen reaction activity and proton transport. Furthermore, a maximum power density of 2.10 W cm ⁻² and an electrolysis current density of −3.23 A cm ⁻² at 1.3 V are achieved for the single cells with the hybrid electrode at 700°C, accompanied by excellent durability over 200 h and reversible cycling stability for 140 h. This work establishes an entropy‐enabled fluorite surface engineering that couples accelerated electrocatalysis with intrinsic humidity resistance, offering a universal strategy for designing next‐generation air electrodes in R‐PCECs.

Direct methanol protonic ceramic fuel cells (PCFCs) offer significant advantages in fuel storage, transportation, and volumetric energy density compared with gaseous hydrogen. However, conventional Ni‐cermet anodes suffer from sluggish methanol reforming kinetics and severe coking at intermediate temperatures. Herein, we develop a novel Ce _0.9 Ru _0.05 Cu _0.05 O _2‐δ (CRCO) anode catalytic layer (ACL) on a Ni‐BaZr _0.4 Ce _0.4 Y _0.1 Yb _0.1 O _3‐δ (Ni‐BZCYYb) anode. Under operating conditions, in situ exsolution yields stable nano‐heterostructures featuring metallic Ru‐Cu‐Ni nanoparticles anchored on the CeO ₂ framework. A Ni‐BZCYYb anode‐supported single cell incorporating the formed catalytic layer delivers a peak power density of 1.05 W cm ⁻² and maintains a stable operation for over 100 h at 0.3 A cm ⁻² at 650°C when fueled with 35% humidified CH ₃ OH. The improved electrochemical performance and coking tolerance can be ascribed to the in situ formed Ru‐Cu‐Ni and ceria oxide heterointerfaces within the ACL and the Ni‐BZCYYb anode, which effectively catalyze methanol decomposition and steam reforming, as corroborated by Raman spectroscopy, exhaust gas analysis, and other post‐operation characterization results. This work demonstrates an effective interfacial engineering strategy for high‐performance, durable direct methanol PCFCs.

Achieving concurrent fast electrode kinetics and long‐term thermo‐mechanical durability remains a critical challenge for reversible protonic ceramic electrochemical cells (R‐PCECs). Herein, we report an interfacial engineering strategy that integrates a perovs.kite‐type PrBaRu _0.1 Co _1.9 O _5+δ (PBRC) nanoparticle layer onto a PrBa _0.5 Sr _0.5 Co _1.5 Fe _0.5 O _5+δ (PBSCF) substrate (PBRC‐PBSCF), together with a modified pellet‐assisted sintering approach to fabricate dense BaZr _0.4 Ce _0.4 Y _0.1 Yb _0.1 O _3‐δ (BZCYYb4411) electrolytes. The in situ reconstructed heterointerface enhances oxygen reduction/evolution reaction (ORR/OER) kinetics, promotes H ₂ O adsorption/dissociation, and improves steam tolerance, as verified by electrochemical measurements and interfacial microstructural analyses. Density functional theory reveals that Ru‐induced electronic modulation at the PBRC‐PBSCF interface lowers the energy of oxygen vacancy formation and optimizes the position of the O 2p band center, thereby accelerating oxygen redox kinetics and stabilizing the interface. The resulting R‐PCECs deliver an excellent peak power density of 1.112 W cm ⁻² and an electrolysis current density of −1.257 A cm ⁻² at 1.3 V in 3% H ₂ O wet air at 600°C, with a reasonable faradaic efficiency. Furthermore, the cells demonstrate excellent stability, sustaining 100 h of thermal cycling (400–600°C, 200°C h ⁻¹ ) in both fuel cell and electrolysis modes, with 600 h of stability in electrolysis mode (600°C, −0.5 to −2 A cm ⁻² ).

Although triple‐conducting (H ⁺ /O ²⁻ /e ⁻ ) cathodes have significantly advanced protonic ceramic fuel cells (PCFCs), limited proton transport and surface cation segregation remain major challenges to commercialization. Here we present a novel atomic layer deposition (ALD)‐enabled reverse atom capture strategy to achieve the in‐situ construction of a protonic conductor on the perovskite cathode. Sn species are first deposited onto PrBa _0.5 Sr _0.5 Co _1.5 Fe _0.5 O _5+δ (PBSCF) via ALD, followed by high‐temperature calcination. Through a reverse atom capture mechanism, Sn selectively captures Ba/Sr from the PBSCF lattice to in‐situ form a (Ba/Sr)SnO _3‐δ (BSS)@PBSCF heterostructure. This design synergistically increases oxygen vacancy concentration in PBSCF and harnesses the high protonic conductivity of BSS, thereby enhancing proton‐involved oxygen reduction reaction kinetics and suppressing cation segregation. The cells with the optimized Sn10‐PBSCF cathode deliver a peak power density of 1.90 W cm ⁻² at 650°C and demonstrate stable operation over 210 h. Density functional theory calculations further reveal a reduced proton migration barrier in BSS. This work introduces an efficient ALD‐enabled reverse atom capture strategy to advance the commercial viability of PCFCs.