The mechanism of water oxidation using transition metal-based heterogeneous electrocatalysts.

The water oxidation reaction, a crucial process for solar energy conversion, has garnered significant research attention. Achieving efficient energy conversion requires the development of cost-effective and durable water oxidation catalysts. To design effective catalysts, it is essential to have a fundamental understanding of the reaction mechanisms. This review presents a comprehensive overview of recent advancements in the understanding of the mechanisms of water oxidation using transition metal-based heterogeneous electrocatalysts, including Mn, Fe, Co, Ni, and Cu-based catalysts. It highlights the catalytic mechanisms of different transition metals and emphasizes the importance of monitoring of key intermediates to explore the reaction pathway. In addition, advanced techniques for physical characterization of water oxidation intermediates are also introduced, for the purpose of providing information for establishing reliable methodologies in water oxidation research. The study of transition metal-based water oxidation electrocatalysts is instrumental in providing novel insights into understanding both natural and artificial energy conversion processes.

Electrocatalytic water oxidation with manganese phosphates.

As inspired by the Mn4CaO5 oxygen evolution center in nature, Mn-based electrocatalysts have received overwhelming attention for water oxidation. However, the understanding of the detailed reaction mechanism has been a long-standing problem. Herein, homologous KMnPO4 and KMnPO4•H2O with 4-coordinated and 6-coordinated Mn centers, respectively, are prepared. The two catalysts constitute an ideal platform to study the structure-performance correlation. The presence of Mn(III), Mn(IV), and Mn(V) intermediate species are identified during water oxidation. The Mn(V)=O species is demonstrated to be the substance for O-O bond formation. In KMnPO4•H2O, the Mn coordination structure did not change significantly during water oxidation. In KMnPO4, the Mn coordination structure changed from 4-coordinated [MnO4] to 5-coordinated [MnO5] motif, which displays a triangular biconical configuration. The structure flexibility of [MnO5] is thermodynamically favored in retaining Mn(III)-OH and generating Mn(V)=O. The Mn(V)=O species is at equilibrium with Mn(IV)=O, the concentration of which determines the intrinsic activity of water oxidation. This study provides a clear picture of water oxidation mechanism on Mn-based systems.

Proton-Coupled Electron Transfer in Electrocatalytic Water Splitting.

Proton-coupled electron transfer (PCET) plays a crucial role in a diverse array of natural and artificial energy conversion processes. Herein, we will introduce the fundamentals of electrochemical PCET with a focus on its role in water splitting. Besides, perspectives of future development of PCET are presented with regard to the investigation of reaction mechanisms and the design of advanced electrocatalysts.

A layered CoSeO3 pre-catalyst for electrocatalytic water oxidation.

In electrocatalytic water oxidation, the surface reconstruction of electrocatalysts is a common issue due to the applied anodic potential. The study of the fundamentals of catalyst structure transformation and the relationship between structure and performance is important. Herein, we designed two cobalt selenites (CoSeO3 and CoSeO3·2H2O) with different structures for comparative studies. The cross channels in layered CoSeO3 provide space for easy surface reconstruction. The reasons are defined by a series of electrochemical studies, indicating a larger ion diffusion coefficient, more surface contacting OH- anions and faster charge transfer kinetics in CoSeO3. This work provided a paradigm for studying the influence of geometric structure on pre-catalyst reconstruction.

Effect of Proton Transfer on Electrocatalytic Water Oxidation by Manganese Phosphates.

The effect of proton transfer on water oxidation has hardly been measurably established in heterogeneous electrocatalysts. Herein, two isomorphous manganese phosphates (NH4 MnPO4 ⋅ H2 O and KMnPO4 ⋅ H2 O) were designed to form an ideal platform to study the effect of proton transfer on water oxidation. The hydrogen-bonding network in NH4 MnPO4 ⋅ H2 O has been proven to be solely responsible for its better activity. The differences of the proton transfer kinetics in the two materials indicate a fast proton hopping transfer process with a low activation energy in NH4 MnPO4 ⋅ H2 O. In addition, the hydrogen-bonding network can effectively promote the proton transfer between adjacent Mn sites and further stabilize the MnIII -OH intermediates. The faster proton transfer results in a higher proportion of zeroth-order in [H+ ] for OER. Thus, proton transfer-affected electrocatalytic water oxidation has been measurably observed to bring detailed insights into the mechanism of water oxidation.

Fungal Interactions Matter: Tricholoma matsutake Domination Affect Fungal Diversity and Function in Mountain Forest Soils.

Tricholoma matsutake forms a symbiotic association with coniferous trees, developing mycelial aggregations, called 'shiro', which are characterized by distinct chemical and physical properties from nearby forest bulk soil. The fungal diversity living in shiro soil play key roles in nutrient cycles for this economically important mushroom, but have not been profiled across large spatial and environmental gradients. Samples of shiro and non-shiro (nearby bulk soil) were taken from five field sites where sporocarps naturally formed. Phospholipid fatty acids (PLFA) and Illumina MiSeq sequencing were combined to identify fungal biomass and community structure. Matsutake dominated in the shiro, which had a significantly reduced saprotrophic fungi biomass compared to non-shiro soil. Fungal diversity was negatively correlated with the relative abundance of T. matsutake in the shiro soil. The fungal community in the shiro was characterized by similar fungal species composition in most samples regardless of forest types. Matsutake coexisted with a specific fungal community due to competition or nutrient interactions. Oidiodendron was positively correlated with the abundance of T. matsutake, commonly cohabitant in the shiro. In contrast, Helotiales and Mortierella were negatively correlated with T. matsutake, both of which commonly inhabit the non-shiro soil but do not occur in shiro soils. We conclude that T. matsutake generate a dominance effect to shape the fungal community and diversity in shiro soil across distinctive forest types.

Autologous manganese phosphates with different Mn sites for electrocatalytic water oxidation.

Herein, we report two autologous phosphates obtained from the same parent material for electrocatalytic water oxidation. These two phosphates have many similarities except the coordination structure of the Mn centers. It has been straightforwardly observed that the highly asymmetric geometry of Mn2P2O7 can stabilize the active Mn(iii) to promote water oxidation.

Microsatellite markers for the prized matsutake mushroom (Tricholoma matsutake, Tricholomataceae).

PREMISE OF THE STUDY: Novel and cost-effective microsatellite markers were developed to explore the population genetics, biogeographic structure, and evolutionary history of the prized Euro-Asian wild edible ectomycorrhizal fungus Tricholoma matsutake (Tricholomataceae). METHODS AND RESULTS: Eighteen new polymorphic simple sequence repeat loci, detected from a microsatellite-enriched genomic library, were used to characterize 131 individuals from eight T. matsutake populations. The number of alleles ranged from two to 10, with averages of 1.42 to 3.22. Levels of observed and expected heterozygosity ranged from 0.00-1.00 and from 0.00-0.83, with mean values of 0.21 and 0.26, respectively. In total, 50% of the loci showed interspecific transferability and polymorphism in the related species T. equestre. CONCLUSIONS: These newly developed markers will aid research into the genetic diversity and population structure of T. matsutake. They can also be used in other species of Tricholoma.

Combination therapy with dendritic cell-based vaccine and anti-CD69 antibody enhances antitumor efficacy in renal cell carcinoma-bearing mice.

BACKGROUND/AIM: Dendritic cell-based vaccine therapy for renal cell carcinoma is effective but requires improvement. Here we explored whether combination therapy with dendritic cell-based vaccine and anti-CD69 antibody can enhance antitumor efficacy in renal cell carcinoma-bearing mice. MATERIALS AND METHODS: Balb/c mice were challenged subcutaneously with murine renal cell carcinoma (Renca) cells. On day 3 after tumor cell inoculation, tumor-bearing mice either were left untreated or were treated with Renca tumor lysate-pulsed dendritic cells (i.e. dendritic cell-based vaccine), anti-CD69 antibody, or a combination of Renca tumor lysate-pulsed dendritic cells with anti-CD69 antibody. The mice were sacrificed on day 28. Tumor volume was measured for analysis of antitumor efficacy. Spleens were excised to evaluate antitumor immunological responses by measuring the proliferation and activation of T cells, which have the capacity to recognize and destroy tumor cells. RESULTS: Combination treatment with Renca tumor lysate-pulsed dendritic cells and anti-CD69 antibody resulted in significant decreases in tumor volume and significant increases in T-cell proliferation and activity, compared with no treatment or either treatment alone. CONCLUSION: These findings indicate that anti-CD69 antibody can potentiate antitumor efficacy of dendritic cell-based vaccine. The augmented therapeutic efficacy conferred by the combination therapy may be associated with increased T-cell proliferation and activity.