Modulating Electronic Structure of Iridium Single-Atom Anchored on 3D Fe-Doped ß-Ni(OH)2 Catalyst with Nanopyramid Array Structure for Enhanced Oxygen Evolution Reaction.

Developing high-performance electrocatalysts for oxygen evolution reaction (OER) is crucial in the pursuit of clean and sustainable hydrogen energy, yet still challenging. Herein, a spontaneous redox strategy is reported to achieve iridium single-atoms anchored on hierarchical nanosheet-based porous Fe doped ß-Ni(OH)2 pyramid array electrodes (SAs Ir/Fe-ß-Ni(OH)2 ), which exhibits high OER performance with a low overpotential of 175 mV at 10 mA cm-2 and a remarkable OER current density in alkaline electrolyte, surpassing Fe-ß-Ni(OH)2 /NF and IrO2 by 31 and 38 times at 1.43 V versus RHE, respectively. OER catalytic mechanism demonstrates that the conversion of * OH→* O and the active lattice O content can be significantly improved due to the modulation effect of the Ir single atoms on the local electronic structure and the redox behavior of FeNi (oxy) hydroxide true active species. This work provides a promising insight into understanding the OER enhancement mechanism for Ir single-atoms modified FeNi-hydroxide systems.

Bi-Functional Co/Al Modified 1T-MoS2 /rGO Catalyst for Enhanced Uranium Extraction and Hydrogen Evolution Reaction in Seawater.

Uranium is a key element in the preparation of nuclear fuel. An electrochemical uranium extraction technique is proposed to achieve high efficiency uranium extraction performance through HER catalyst. However, it is still a challenge to design and develop a high-performance hydrogen evolution reaction (HER) catalyst for rapid extraction and recovery of uranium from seawater. Herein, a bi-functional Co, Al modified 1T-MoS2 /reduced graphene oxide (CA-1T-MoS2 /rGO) catalyst, showing a good HER performance with a HER overpotential of 466 mV at 10 mA cm-2 in simulated seawater, is first developed. Benefiting from the high HER performance of CA-1T-MoS2 /rGO, efficient uranium extraction is achieved with a uranium extraction capacity of 1990 mg g-1 in simulated seawater without post-treatment, exhibiting a good reusability. The results of experiments and density functional theory (DFT) show that a high uranium extraction and recovery capability is attributed to the synergy effect of the improved HER performance and the strong adsorption capacity between U and OH*. This work provides a new strategy for the design and preparation of bi-functional catalysts with high HER performance and uranium extraction and recovery capabilities in seawater.

Novel FeNi-Based Nanowires Network Catalyst Involving Hydrophilic Channel for Oxygen Evolution Reaction.

Developing novel, efficient, and low-cost 3D FeNi-based oxygen evolution reaction (OER) catalysts with the special hydrophilic channel is still a challenge for improving hydrogen production efficiency. Herein, a novel 3D ethoxy substituted FeNi oxalate (ENWs-FeNi-C2 O4 ) nanowires network catalyst with hydrophilic channels is reported firstly, which shows an outstanding OER activity with a low overpotential (215 mV at 10 mA cm-2 ) and small Tafel slope (54.5 mV dec-1 ). OER catalytic mechanism indicates that the OH adsorption step and O2 bubble diffusion step of OER reaction process can be significantly improved due to the special hydrophilic channels, and the ethoxy as an interlayer ligand not only expands the interlayer distance of layered FeNi (oxy) hydroxide true active species but modulates its electronic structure, promoting the *OOH formation step, and thus exhibiting the outstanding OER performance. This work provides a novel idea for the preparation of novel and efficient OER electro-catalysts with special 3D structures.

Porous Fe-Doped ß-Ni(OH)2 Nanopyramid Array Electrodes for Water Splitting.

We report a highly efficient and stable electrode composed of a porous Fe-doped ß-nickel hydroxide nanopyramid array supported on nickel foam (U-Fe-ß-Ni(OH)2/NF) for overall water splitting. The unique structure is assembled via a self-templated strategy by utilizing the FeNi oxalate (FeNi-C2O4/NF) nanopyramid as the templates, followed by an anion-exchange reaction at room temperature. Due to the intrinsic activity of Fe-doped ß-Ni(OH)2 along with unique porous array structures consisting of two-dimensional (2D) active materials on three-dimensional (3D) conductive substrates, the developed electrode exhibited outstanding electrocatalytic activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline medium. The introduced amount of Fe plays a significant role in promoting OER and HER activity compared to the ß-Ni(OH)2 electrode. The optimal electrode (U-Fe-ß-Ni(OH)2/NF-2) generated a current density of 10 mA cm-2 at low overpotentials of 218 mV for the OER and 121 mV for the HER. The electrode also demonstrated considerably stable performance during the continuous water splitting process. Furthermore, we elucidated the promotion mechanisms of the active Fe-doped ß-Ni(OH)2 compound for the OER and HER based on extensive characterization and electrochemical measurements. Hence, this work provides a facile approach to developing low-cost, efficient, and stable hydroxide-based electrodes for bifunctional OER and HER in water splitting.