Surface-Modified Ruthenium Nanorods for an Ampere-Level Bifunctional Hydrogen Evolution Reaction/Oxygen Evolution Reaction Electrocatalyst.

The practical applications of bifunctional ruthenium-based electrocatalysts with two active sites of Ru nanoparticles covered with RuO2 skins are limited. One reason is the presence of multiple equally distributed facets, some of which are inactive. In contrast, ruthenium nanorods with a high aspect ratio have multiple unequally distributed facets containing the dominance of active faces for efficient electrocatalysis. However, the synthesis of ruthenium nanorods has not been achieved due to difficulties in controlling the growth. Additionally, it is known that the adsorption capacity of intermediates can be impacted by the surface of the catalyst. Inspired by these backgrounds, the surface-modified (SM) ruthenium nanorods having a dominant active facet of hcp (100) through chemisorbed oxygen and OH groups (SMRu-NRs@NF) are rationally synthesized through the surfactant coordination method. SMRu-NRs@NF exhibits excellent hydrogen evolution in acid and alkaline solutions with an ultralow overpotential of 215 and 185 mV reaching 1000 mA cm-2, respectively. Moreover, it has also shown brilliant oxygen evolution electrocatalysis in alkaline solution with a low potential of 1.58 V to reach 1000 mA cm-2. It also exhibits high durability over 143 h for the evolution of oxygen and hydrogen at 1000 mA cm-2. Density functional theory studies confirmed that surface modification of a ruthenium nanorod with chemisorbed oxygen and OH groups can optimize the reaction energy barriers of hydrogen and oxygen intermediates. The surface-modified ruthenium nanorod strategy paves a path to develop the practical water splitting electrocatalyst.

Platinum Nanoparticles Bonded with Carbon Nanotubes for High-Performance Ampere-Level All-Water Splitting.

Platinum nanoparticles loaded on a nitrogen-doped carbon nanotubes exhibit a brilliant hydrogen evolution reaction (HER) in an alkaline solution, but their bifunctional hydrogen and oxygen evolution reaction (OER) has not been reported due to the lack of a strong Pt-C bond. In this work, platinum nanoparticles bonded in carbon nanotubes (Pt-NPs-bonded@CNT) with strong Pt-C bonds are designed toward ultralow overpotential water splitting ability in alkaline solution. Benefit from the strong interaction between platinum and high conductivity carbon nanotube substrates through the Pt-C bond also the platinum nanoparticles bonded in carbon nanotube can provide more stable active sites, as a result, the Pt-NPs-bonded@CNT exhibits excellent hydrogen evolution in acid and alkaline solution with ultralow overpotential of 0.19 and 0.23 V to reach 1000 mA cm-2, respectively. Besides, it shows superior oxygen evolution electrocatalysis in alkaline solution with a low overpotential of 1.69 V at 1000 mA cm-2. Furthermore, it also exhibits high stability over 110 h against the evolution of oxygen and hydrogen at 1000 mA cm-2. This strategy paves the way to the high performance of bifunctional electrocatalytic reaction with extraordinary stability originating from optimized electron density of metal active sites due to strong metal-substrate interaction.

Reactive Epitaxial Formation of a Mg-P-Zn Ternary Semiconductor in Mg/Zn3P2 Solar Cells.

Zinc phosphide (Zn3P2) has attracted considerable attention as an environmentally benign and earth-abundant photoabsorber for thin-film photovoltaics. It is known that interdiffusion occurs at the Mg/Zn3P2 interface, which is a component of the record device, but the micro- and nanoscopic structures of the interface after interdiffusion have been controversial for over three decades. Here, we report on the formation of a Mg-P-Zn ternary semiconductor, Mg(Mg xZn1- x)2P2, at the Mg/Zn3P2 interface. Interestingly, Mg(Mg xZn1- x)2P2 is epitaxially grown on Zn3P2 with the orientation relationship of [21̅1̅0](0001)Mg(Mg xZn1- x)||[100](011)Zn3P2 due to interdiffusion. The lattice mismatch of the Mg(Mg xZn1- x)2P2 layer on the Zn3P2 substrate is less than 0.5%, and this is favorable for carrier transport across the interface. Mg(Mg xZn1- x)2P2 is the material suggested as "n-type Mg-doped Zn3P2" or "a Mg-P-Zn alloy" in the previous studies. Thus, only the optimization of Mg treatment as conducted in the previous studies is insufficient for the improvement of the cell performance. This work clarified that a suitable microstructure and band structure around Mg(Mg xZn1- x)2P2/Zn3P2 heterointerface should be established.