Surface Defect Engineering on Perovskite Oxides as Efficient Bifunctional Electrocatalysts for Water Splitting.

The design of high-performance and cost-effective electrocatalysts for water splitting is of prime importance for efficient and sustainable hydrogen production. In this work, a surface defect engineering method is developed for optimizing the electrocatalytic activity of perovskite oxides for water electrolysis. A typical ferrite-based perovskite oxide material La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is used and regulated by selective acid etching. The optimal parameters for the surface treatment are identified. An efficient bifunctional perovskite oxide, denoted LSCF-30, is prepared by selectively corroding the A-site Sr element in the surface region, which is found to not only increase the exposure and decrease the coordination of B-site metals but also effectively modulate the electronic structure of these metals. The crystal lattice of the perovskite bulk is kept constant during surface engineering, which ensures the structural stability of the perovskite catalyst. The findings demonstrate an effective strategy of surface defect engineering in enhancing the performance of perovskite oxide electrocatalysts for water splitting.

Ag-Embedded Silica Core-Shell Nanospheres for Operando Surface Enhanced Raman Spectroscopy of High-Temperature Processes.

The construction of thermally robust, highly active, and universal substrate architectures is a major challenge for high-temperature operando studies using surface enhanced Raman spectroscopy (SERS). Herein, a novel hybrid nanostructure of embedded Ag nanoparticles confined by a core-shell silica nanosphere through facile chemical synthesis is reported. Benefiting from the coupling effect of embedded Ag nanojunctions and the nanoconfinement of the silica core-shell, the hybrid nanospheres exhibit strong SERS-enhancement effects and thermal stability without restrictions on the substrate generality. Three-dimensional finite-difference time-domain (3D-FDTD) calculation indicates that the self-assembled nanojunctions of the embedded Ag nanoparticles facilitate a strong amplification of the electromagnetic field on individual nanospheres. The measurements on the trace analysis of the carbon species and dynamic tracking of the ceria lattice illustrate the feasibility of the hybrid nanospheres for the operando analysis of high-temperature processes, especially for trace detection of critical surface species or dynamic tracking of local structure evolution.

Electrochemically Scavenging the Silica Impurities at the Ni-YSZ Triple Phase Boundary of Solid Oxide Cells.

Silica impurity originated from the sealing or raw materials of the solid oxide cells (SOCs) accumulating at the Ni-YSZ triple phase boundaries (TPBs) is known as one major reason for electrode passivation. Here we report nanosilica precipitates inside Ni grains instead of blocking the TPBs when operating the SOCs at |i| ≥ 1.5 A cm(-2) for electrolysis of H2O/CO2. An electrochemical scavenging mechanism was proposed to explain this unique behavior: the removal of silica proceeded through the reduction of the silica to Si under strong cathodic polarization, followed by bulk diffusion of Si into Ni and reoxidation of Si in the Ni grain.