As fossil energy sources gradually deplete, the global demand for energy transformation is becoming increasingly urgent. Proton Ceramic Electrolyte Cells (PCECs), as a novel energy conversion device, are demonstrating significant potential in the field of clean energy. Compared to traditional Solid Oxide Electrolysis Cells, PCECs have gained widespread attention in recent years due to their low operating temperature and advantages in gas separation. In PCECs, when water vapor is introduced into the steam electrode and a certain voltage is applied, the fuel electrode is capable of producing high-purity hydrogen gas. Despite the widespread attention on PCECs, the stability of the steam electrode under high-humidity conditions remains a major obstacle to their large-scale commercial application. Over the past decade, many studies have focused on improving the stability of PCECs. Although certain progress has been made through modification methods such as doping, these advancements still do not meet the requirements for commercial applications.

Recently, a team of material scientists led by Lin Ge from Nanjing Tech University, China, reported the first composite steam electrode for Protonic Ceramic Electrolysis Cells (PCECs). This electrode consists of a double perovskite PrBaMn₂O_5+δ (PBM) and a durable proton conductor BaZr_0.85Y_0.15O_3-δ (BZY), with in situ deposition of nano PrO_x catalysis. Phase structure (XRD, SEM, TEM) and electrochemical performance (EIS, thermal expansion coefficients, total conductivity and electrolysis current) analyses have demonstrated that the composite steam electrode exhibits excellent stability and superior electrical performance. This work not only highlights the advantages of the composite steam electrodes but also confirms the superior proton conduction of the cube-shaped BZY/PBM interface compared to nanosized BZY.

“In this article, we report a novel composite steam electrode for Protonic Ceramic Electrolysis Cells (PCECs) that demonstrates exceptional durability and superior electrical performance. The composite steam electrode is composed of double perovskite PBM, cube-shaped proton conductor BZY, and in situ deposited nano PrO_x catalysis. The electrode exhibits remarkable durability under high water vapor concentrations and constant current density. Our findings present a promising strategy for designing durable steam electrodes for PCECs through a rational compositional approach.” said Lin Ge, professor at College of Materials Science and Engineering at Nanjing Tech University (China), a senior expert whose research interests focus on the field of proton ceramic electrochemical cells.

“Notably, the facet-boosted interface engineering significantly enhances efficient proton transfer within the composite steam electrode. The electrode composed of cube-shaped BZY microcrystals and PBM demonstrates significantly higher proton conductivity, with an entire order of magnitude improvement compared to electrodes made with nanosized BZY. Our investigation about cube-shaped BZY and nanosized BZY exemplifies efficient MIEC/proton conductor interface design.” said Lin Ge.

Sign up for the Daily Dose Newsletter and get every morning’s best science news from around the web delivered straight to your inbox? It’s easy like Sunday morning.

Cube-shaped BZY exhibits higher proton conductivity and larger grain size (>1μm) than nanosized BZY. “In our previous research, we found that cube-shaped BZY exhibited superior conductivity and enhanced durability against Ba evaporation and Y segregation. Additionally, the cube-shaped BZY/PBM interface may offer an extra pathway for proton conduction in composite steam electrodes. Our findings complement and extend the ‘job-sharing’ mechanism in the field of electrochemistry, providing valuable insights into the design of efficient composite electrodes.” said Lin Ge.

PBM-BZY-PrO_x composite steam electrode exhibits reliable total conductivity and excellent stability in high humidity. The thermal expansion coefficient (TEC) of PBM-BZY-PrO_x composite steam electrode is 11.51×10⁻⁶ K⁻¹, which is much closer to that of the electrolyte. “The TEC is expected to improve electrode-electrolyte interfacial contact and enhance long-term operational durability.” said Lin Ge.