Rechargeable Zn-air batteries have attracted great attention owing to their high energy densities, environmental friendliness, and low costs, in which the oxygen evolution reaction (OER) determines the charging efficiency. Recently, the development of efficient oxygen electrocatalysts has been seen as pivotal in realizing practical Zn-air batteries. Transition metal oxides are important oxygen electrocatalysts. However, the conventional adsorbate evolution mechanism (AEM) induces a valence change in the transition metal and even surface reconstruction during the OER, which results in behaviors typical of zinc-ion batteries, specifically, the emergence of two voltage platforms. To address this issue, the precise design of advanced oxygen electrocatalysts for rechargeable Zn-air batteries is imperative.
On November 1, 2023, the study entitled "Accelerated deprotonation with a hydroxyl-silicon alkali solid for rechargeable zinc-air batteries" was published online in Nature Communications (https://www.nature.com/articles/s41467-023-42728-y).The research was completed by Prof. Yunfei Bugroup of Nanjing University of Information Engineering in cooperation with Curtin University of Australia and Southern University of Science and Technology. Their previous study found that the surface functionalized Lewis base as an electron-pair donor and efficiently coordinated with protons could reduce the energy barrier of OOH* deprotonation process, thus successfully overcoming the limitation of proton transfer kinetics in OER process. Silicon compounds exhibit excellent electrochemical stability in alkaline media and possess the best Gibbs free energy of H adsorption, making them ideal proton acceptors for efficient H adsorption/desorption.
In this study, BaCaSiO4 nanoparticles with hydroxyl groupswere successfully integrated onto the PrBa0.5Ca0.5Co2O5+δsurface by a simple one-step in situ exsolution method. BCS-PBCC exhibits a low overpotential of 300 mV (current density@10 mA cm-2) in an ambient of 1.0 M KOH. By in-situ differential electrochemical mass spectrometry (DEMS) measurements, the researchers quantified that some of the O atoms in OER originate from the perovskite lattice. Density functional theory calculations reveal that a proton transfer mechanism involving hydroxyl and lattice oxygen (OH-Si-LOM) occurs at the BCS-PBCC interface. This unique hydroxyl silicon structure (HO-Si-O-Ca2+/Ba2+-O-Si-OH) facilitates the deprotonation process of OH* adsorbed on the perovskite surface. In the assembled zinc-air battery, the researchers observed that the battery exhibited a low charge voltage of 1.93 V at a current density of 50 mA cm–2. This study not only shows the possibility of optimizing the electrocatalytic activity through silicon-based compounds, but also provides valuable theoretical and practical experience for further development of high-efficiency and low-cost zinc-air batteries.
This study was mainly conducted by Nanjing University of Information Science & Technology. Professor Yunfei Bu and Professor Qian Lu from the School of Environmental Science and Engineering at Nanjing University of Information Science & Technology, Professor Zongping Shao from Curtin University and Professor Caichao ye from Southern University of Science and Technology were the co-corresponding authors. Dr. Yaobin Wang from the School of Environmental Science and Engineering at Nanjing University of Information Science & Technology was the first author of the paper.
TheNature Communications paper reports that adjusting orbital electrons to balance hydrogen adsorption/desorption.
Because of its potential value in efficient and scalable hydrogen production, water splitting via the electrochemical hydrogen evolution reaction (HER) has attracted considerable attention from industrial and scientific communities. Even though they are the heart of hydrogen evolution catalysis, catalysts with satisfactory performance are still rare, despite the tremendous effort that has been devoted to improving HER catalysts. Among various approaches, sulfur (S) vacancies and strain have been introduced to activate and optimize the basal plane of monolayer 2H–MoS2, leading to the highest intrinsic HER activity among molybdenum–sulfide-based catalysts. A high concentration of strained metallic 1T WS2 sites, obtained by chemical exfoliation, led to WS2 nanosheets with enhanced catalytic activity. Ultrathin Pt nanowires on singlelayered Ni(OH)2 nanosheets with a unique hybrid nanostructure were also achieved, and exhibited unprecedented catalytic activity and stability toward HER. Nonetheless, in spite of these achievements, strategic exploration to improve the HER performance of catalysts is still a great challenge.
OnSeptember 6, 2019, the study entitled " Balancing hydrogen adsorption/desorption by orbital modulation for efficient hydrogen evolution catalysis" was published online in Nature Communications (https://www.nature.com/articles/s41467-019-12012-z).The research was completed by Prof. Yunfei Bugroup of Nanjing University of Information Engineering in cooperation with Ulsan National Institute of Science and Technology of South Korea, Chongqing University and University of Science and Technology of China.
In this study, we report the rational design of an efficient catalyst for hydrogen evolution, by balancing hydrogen adsorption/desorption via orbital modulation. Theoretical calculations suggested that the d orbitals of Ir sites can be manipulated through strong interactions with the p orbitals of C/N atoms. They suggested that orbital modulation would further balance the hydrogen adsorption/desorption behaviors of the surficial Ir sites, enabling efficient hydrogen evolution. Inspired by the theoretical results, IrHNC was prepared by anchoring a low content of IrNP on nitrogenated carbon matrixes. As expected, the IrHNC exhibited significantly enhanced reaction kinetics, mass activity and intrinsic activity for the hydrogen evolution. This work not only highlights the rational design of a catalyst for efficient hydrogen evolution, but also introduces an opportunity to achieve enhanced catalytic performance for diverse reactions via orbital modulation.
Professor Yunfei Bu from the School of Environmental Science and Engineering at Nanjing University of Information Science & Technology, Professor Zhengping Fu and Professor Yalin Lu from University of Science and Technology of China and Professor Jong-Beom Baek from Ulsan National Institute of Science and Technology of South Korea were the co-corresponding authors. Dr. Feng Li from Ulsan National Institute of Science and Technology of South Korea was the first author of the paper.
The Nature Communications paper reports that first preparation and identification of novel Zn-N2 active sites and the research on structural activation.
Active sites are at the heart of catalysts, while the nature of active sites plays a key role in the performance of catalysts. During the past decade, the active sites of transition metal–nitrogen–carbon (TMNC) catalysts have not been well identified and are simply defined as TM-Nx based on information from X-ray photoelectron spectroscopy (XPS). Such rough recognition of active sites leads to ambiguous understanding of the reaction mechanisms occurring on the surface of the catalysts, as well as stagnation of the development of rational catalyst design strategies. Recently, synchrotron radiation-based extended X-ray absorption fine structure (EXAFS) spectrum analysis, along with experimental characterization and theoretical simulation, has gradually been introduced to identify the geometric structures of active sites. Despite this progress, however, the more structurally sensitive X-ray absorption near edge structure (XANES) spectrum analysis has been neglected. To obtain fundamental understanding of active sites and catalytic mechanisms, identifying the electronic and geometric structures of active sites with both XANES and EXAFS spectra is still highly desired.
On June 13, 2019, the study entitled " Identifying the structure of Zn-N2 active sites
and structural activation" was published online in Nature Communications (https://www.nature.com/articles/s41467-019-10622-1).The research was completed by Prof. Yunfei Bugroup of Nanjing University of Information Engineering in cooperation with Ulsan National Institute of Science and Technology of South Korea, University of Science and Technology of China, Jiangsu University and Nanjing University of Science and Technology.
In this study, Zn-N2 active sites have been achieved and identified by both EXAFS and XANES spectra. Theoretical calculations reveal that the structural activation of oxygen species on Zn-N2 active sites is favoured by the selective oxygen reduction, which is confirmed by the experimental results. This work not only achieves the preparation and identification of Zn-N2 active sites but also provides a regular principle to obtain deep insight into the nature of catalysts for various catalytic applications.
Professor Yunfei Bu from the School of Environmental Science and Engineering at Nanjing University of Information Science & Technology, Professor Zhengping Fu from University of Science and Technology of China and Professor Jong-Beom Baek and Professor Hu Young Jeong from Ulsan National Institute of Science and Technology of South Korea were the co-corresponding authors. Dr. Feng Li from Ulsan National Institute of Science and Technology of South Korea was the first author of the paper.
