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Hydrogen and other renewable resources derived by sunlight have attracted great attention to sustainable development. But the photochemical performance of diverse systems is restricted because of the poor efficiency of photon absorption, easy recombination of photogenerated electron–hole pairs, and slow transfer of charge carriers. Single-atom catalysts (SACs), in which isolated atoms are supported on the supports without forming nanoparticles, have received increasing interests in photocatalysis due to the high catalytic activity, selectivity, stability, and 100% atom utilization. In this review, we highlight and introduce recent advances in the preparation method of SACs and concrete examples of single-atom photocatalysts used for the hydrogen evolution from water, overall water splitting, CO2 and N2 reduction reaction. At last, we discuss the underlying mechanisms for photocatalytic performance of single-atom catalysts and the prospects for the development of SACs.

Numerous studies suggested that oxidative stress (OS) played a central role in the onset and development of postmenopausal osteoporosis (PO); however, conflicting results were obtained as to the association of OS-related biomarkers and PO. This meta-analysis aimed to identify the association between these markers and PO, and explore factors that may explain the inconsistencies in these results. A systematic literature search was conducted in relevant database. Search terms and selection criteria were priorly determined to identify and include all studies that detected markers of OS in PO patients. We pooled data with a random effects meta-analysis with standardized mean differences and 95% confidence interval. Total 17 studies including 12 OS markers were adopted. The results showed that superoxide dismutase (SOD) in erythrocytes, catalase (CAT), total antioxidant status (TAS), hydroperoxides (HY), advanced oxidation protein products (AOPP), malondialdehyde (MDA), and vitamin B12 (VB12) in plasma/serum were not statistically different between the PO and control group, whereas significantly increased level of homocysteine (Hcy) and nitric oxide (NO), along with decreased SOD, glutathione peroxidase (GPx), folate, and total antioxidant power (TAP) in plasma/serum were obtained in the PO group. In summary, OS might serve as potential biomarkers in the etiopathophysiology and clinical course of PO.

Background: Osteoblast apoptosis induced by oxidative stress plays a crucial role in the development and progression of osteoporosis. Curcumin, a natural antioxidant isolated from Curcuma longa, has highly protective effects against osteoporosis. However, the effects of curcumin on oxidative stressinduced osteoblast apoptosis remain unclear. This study aimed to explore the effect of curcumin on hydrogen peroxide (H 2 O 2 ) induced osteoblast apoptosis and the underlying mechanisms. Methods: An osteoblastic cell line (Saos-2) was exposed to various concentrations of H 2 O 2 with or without curcumin treatment. Cell viability was evaluated by MTT assays. The apoptosis rate was analyzed by flow cytometry and TUNEL assays. Mitochondrial ROS and membrane potential were determined using a fluorescence microscope. Mitochondrial respiratory enzyme activity was measured using a spectrophotometer. Protein levels were detected by western blotting. Results: Curcumin was cytoprotective because it greatly improved the viability of Saos-2 cells exposed to H 2 O 2 and attenuated H 2 O 2 -induced apoptosis. Curcumin treatment also preserved the mitochondrial redox potential, decreased the mitochondrial oxidative status, and improved the mitochondrial membrane potential and functions. Furthermore, curcumin treatment markedly increased levels of phosphorylated protein kinase B (Akt) and phosphorylated glycogen synthase kinase-3β (GSK3β). Conclusion: Curcumin administration ameliorates oxidative stress-induced apoptosis in osteoblasts by preserving mitochondrial functions and activation of Akt-GSK3β signaling. These data provide experimental evidence supporting the clinical use of curcumin for prevention or treatment of osteoporosis.P. Dai and Y. Mao contributed equally to this work.

Water molecular adsorption, intermediate species transformation, and product desorption are three main steps for the water splitting that are subject to the corresponding factors of surface wettability, exposed active sites, and mass transfer, respectively. Suitable catalyst with the tailored architecture should be highly regarded to optimize the consistency and systematicness of these three procedures. Herein, highly hydrophilic heteroporous MoS 2 /Ni 3 S 2 on nickel foam (p-MoS 2 /Ni 3 S 2 /NF) is fabricated through a two-steps strategy including electrodeposition and solvothermal reaction. Intensive water affinity relevant with the porous structure and composition is identified by the contact angle test. Electrochemical surface area results demonstrate the upsurge of active sites for the porous structure in comparison with other samples. The fast mass diffusion feature of the p-MoS 2 /Ni 3 S 2 /NF catalyst is further proved by the multistep chronoamperometric for HER and OER process. Attributed to the above nature superiorities, the electrochemical activity of this p-MoS 2 /Ni 3 S 2 /NF has been greatly enhanced. The overpotentials at a geometric current density of 10 mA cm −2 for OER and HER significantly reduce to 185 mV and 99 mV in alkaline media, respectively. The as-prepared catalyst p-MoS 2 /Ni 3 S 2 /NF only needs the cell voltages of 1.50, 1.62, and 1.71 V at current densities of 10, 20, and 50 mA cm −2 to drive water splitting and performs with the good stability for at least 48 h in total. This fascinating material is designed by multiscale principles that stemmed from a better insight on the structure−activity relationship, and it can also afford constructive inspirations for the forward development of various catalytic reactions.

The present work reports a general approach to improve the electrocatalytic property of noble metal through regulating its electron status by introducing the electronic metal–support interaction (EMSI). As a case study, the catalytic activity of metallic Pd toward oxygen evolution reaction (OER) in alkaline solution has been significantly promoted by stabilizing Pdδ+ oxidic species at the interface of the Pd–metal oxide support with the help of EMSI effect, suggesting an intrinsic advantage of Pdδ+ in driving OER. We further demonstrate that the chemical state of Pdδ+ can be easily modulated in the range of 2+ to 3+ by changing the metal oxide support, interestingly, accompanied by a clear dependence of the OER activity on the oxidation state of Pdδ+. The high Pd3+ species-containing Fe2O3/Pd catalyst has fed an impressively enhanced OER property, showing an overpotential of 383 mV at 10 mA cm–2 compared to those of >600 mV on metallic Pd and 540 mV on Fe2O3/glassy carbon. The greatly enhanced OER performance is believed to primarily derive from the distinctive improvement in the adsorption of oxygenated intermediates (e.g., *OH and *OOH) on metal-oxide/Pd catalysts. Moreover, similar EMSI induced improvements in OER activity in alkaline solution are also achieved on both of the Fe2O3/Au and Fe2O3/Pt, which possess the oxidic species of Au3+, and Pt2+ and Pt4+, respectively.

The heteroporous MoS2/Ni3S2 catalyst exhibits excellent electrocatalytic activity for the overall urea splitting with only a cell voltage of 1.45 V at 20 mA cm-2 in 1 M KOH with 0.33 M urea. This value is the best of all the bifunctional urea splitting electrocatalysts, including Pt, reported to date.

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