How to Change the Reaction Chemistry on Nonprecious Metal Oxide Nanostructure Materials for Electrocatalytic Oxidation of Biomass-Derived Glycerol to Renewable Chemicals.

Au and Pt are well-known catalysts for electrocatalytic oxidation of biomass-derived glycerol. Although some nonprecious-metal-based materials to replace the costly Au and Pt are used for this reaction, the fundamental question of how the nonprecious catalysts affect the reaction chemistry and mechanism compared to Au and Pt catalysts is still unanswered. In this work, both experimental and computational methods are used to understand how and why the reaction performance and chemistry for the electrocatalytic glycerol oxidation reaction (EGOR) change with electrochemically-synthesized CuCo-oxide, Cu-oxide, and Co-oxide catalysts compared to conventional Au and Pt catalysts. The Au and Pt catalysts generate major glyceric acid and glycolic acid products from the EGOR. Interestingly, the prepared Cu-based oxides produce glycolic acid and formic acid with high selectivity of about 90.0%. This different reaction chemistry is related to the enhanced ability of CC bond cleavage on the Cu-based oxide materials. The density functional theory calculations demonstrate that the formic acids are mainly formed on the Cu-based oxide surfaces rather than in the process of glycolic acid formation in the free energy diagram. This study provides critical scientific insights into developing future nonprecious-based materials for electrochemical biomass conversions.

Perovskite-based electrocatalysts for oxygen evolution reaction in alkaline media: A mini review.

Water electrolysis is one of the attractive technologies for producing clean and sustainable hydrogen fuels with high purity. Among the various kinds of water electrolysis systems, anion exchange membrane water electrolysis has received much attention by combining the advantages of alkaline water electrolysis and proton exchange membrane water electrolysis. However, the sluggish kinetics of the oxygen evolution reaction, which is based on multiple and complex reaction mechanisms, is regarded as a major obstacle for the development of high-efficiency water electrolysis. Therefore, the development of high-performance oxygen evolution reaction electrocatalysts is a prerequisite for the commercialization and wide application of water electrolysis systems. This mini review highlights the current progress of representative oxygen evolution reaction electrocatalysts that are based on a perovskite structure in alkaline media. We first summarize the research status of various kinds of perovskite-based oxygen evolution reaction electrocatalysts, reaction mechanisms and activity descriptors. Finally, the challenges facing the development of perovskite-based oxygen evolution reaction electrocatalysts and a perspective on their future are discussed.

Unveiling the enhanced electrocatalytic activity at electrochemically synthesized Pt-WOx hybrid nanostructure interfaces.

Here we report a simple synthesis strategy for Pt-WOx hybrid nanostructures using a metal-dissolution-based electrodeposition technique. The hybrid nanostructures demonstrate an excellent catalytic hydrogen evolution reaction performance with an approximately 17 times higher Pt mass activity and a 7.4 times higher turnover frequency than those of commercial Pt catalysts. The enhanced electrocatalytic performance is related to the creation of Pt-WOx interfacial sites.

1-D structured flexible supercapacitor electrodes with prominent electronic/ionic transport capabilities.

A highly efficient 1-D flexible supercapacitor with a stainless steel mesh (SSM) substrate is demonstrated. Indium tin oxide (ITO) nanowires are prepared on the surface of the stainless steel fiber (SSF), and MnO2 shell layers are coated onto the ITO/SSM electrode by means of electrodeposition. The ITO NWs, which grow radially on the SSF, are single-crystalline and conductive enough for use as a current collector for MnO2-based supercapacitors. A flake-shaped, nanoporous, and uniform MnO2 shell layer with a thickness of ~130 nm and an average crystallite size of ~2 nm is obtained by electrodeposition at a constant voltage. The effect of the electrode geometry on the supercapacitor properties was investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and a galvanostatic charge/discharge study. The electrodes with ITO NWs exhibit higher specific capacitance levels and good rate capability owing to the superior electronic/ionic transport capabilities resulting from the open pore structure. Moreover, the use of a porous mesh substrate (SSM) increases the specific capacitance to 667 F g(-1) at 5 mV s(-1). In addition, the electrode with ITO NWs and the SSM shows very stable cycle performance (no decrease in the specific capacitance after 5000 cycles).

Controlled interfacial electron dynamics in highly efficient Zn2 SnO4 -based dye-sensitized solar cells.

Among ternary oxides, Zn2 SnO4 (ZSO) is considered for dye-sensitized solar cells (DSSCs) because of its wide bandgap, high optical transmittance, and high electrical conductivity. However, ZSO-based DSSCs have a poor performance record owing largely to the absence of systematic efforts to enhance their performance. Herein, general strategies are proposed to improve the performance of ZSO-based DSSCs involving interfacial engineering/modification of the photoanode. A conformal ZSO thin film (blocking layer) deposited at the fluorine-doped tin oxide-electrolyte interface by pulsed laser deposition suppressed the back-electron transfer effectively while maintaining a high optical transmittance, which resulted in a 22 % improvement in the short-circuit photocurrent density. Surface modification of ZSO nanoparticles (NPs) resulted in an ultrathin ZnO shell layer, a 9 % improvement in the open-circuit voltage, and a 4 % improvement in the fill factor because of the reduced electron recombination at the ZSO NPs-electrolyte interface. The ZSO-based DSSCs exhibited a faster charge injection and electron transport than their TiO2 -based counterparts, and their superior properties were not inhibited by the ZnO shell layer, which indicates their feasibility for highly efficient DSSCs. Each interfacial engineering strategy could be applied to the ZSO-based DSSC independently to lead to an improved conversion efficiency of 6 %, a very high conversion efficiency for a non-TiO2 based DSSC.

Reduction process of dislocation and standby leakage current for embedded flash memory using nano-scale integration.

We determined that the use of densification, sacrificial oxidation, gate oxidation and source/drain implantation has the capability to reduce the dislocation. A dislocation-free process is proposed, and its mechanism presented in embedded flash memory. The dislocation decreased when n-type ions were implanted at a low energy level for source and drain. A dry oxidation process using only oxygen without hydrogen and oxidation for logic gates led to the formation of a sacrificial oxide on the rapid thermal oxidation (RTP) methods without densification after gap-filling as reducing dislocation processes. These methods dramatically reduced the standby leakage current.