Partially selenized FeCo layered double hydroxide as bifunctional electrocatalyst for efficient and stable alkaline (sea)water splitting.

Seawater electrolysis to produce hydrogen is a clean and sustainable strategy for the development of clean and sustainable energy storage systems. However, the erosion and destruction of electrocatalysts of the devices by Cl- in seawater during splitting process make it very difficult to realize. In this work, a partially selenized FeCo layered double hydroxide (Se-FeCo-LDH) catalyst is successfully synthesized, which shows good electrocatalytic performance in seawater during water splitting due to both its excellent conductivity and large surface area. Moreover, an anion aggregation layer around the electrode during the catalytic process can be formed to avoid electrode erosion and destruction by Cl- as well as the competitive reaction of chloride oxidation with the oxygen evolution reaction (OER), which not only improves the catalytic efficiency but also the durability of the catalyst. As a result, the overpotential is only 229 mV at a current density of 100 mA cm-2 for OER in 1 M KOH. Only 1.446 V and 1.491 V voltages are required to reach a current density of 10 mA cm-2 in overall alkaline water and seawater splitting, respectively. Besides, this Se-FeCo-LDH catalyst also achieves long-term stability up to 245 h in overall alkaline seawater splitting. The development of Se-FeCo-LDH catalyst should have an enlightening effect in the field of hydrogen production by (sea)water electrolysis.

Coupling heterostructured CoP-NiCoP nanopin arrays with MXene (Ti3C2Tx) as an efficient bifunctional electrocatalyst for overall water splitting.

Developing a highly effective bifunctional electrocatalyst for alkaline-condition electrochemical water splitting is both essential and challenging. The work presented here successfully synthesizes and employs a heterostructured CoP-NiCoP ultra-long nanopin array in situ growing on MXene (Ti3C2Tx) as a stable bifunctional electrocatalyst for electrochemical water-splitting. The heterogeneous structure formed by CoP nanoparticles and NiCoP nanopins provides extra active sites for water-splitting. Also, Ti3C2Tx works as a support substrate during electrochemical operations, accelerating mass transfer, ion transport, and rapid gas product diffusion. Meanwhile, throughout the catalytic process, the dense nanopin arrays shield Ti3C2Tx from further oxidation. At a result, the CoP-NiCoP-Ti3C2Tx (denoted as CP-NCP-T) demonstrated excellent catalytic activity, with overpotentials of just 46 mV for hydrogen evolution at 10 mA cm-2 and 281 mV for oxygen evolution at 50 mA cm-2. Furthermore, in 1.0 M KOH solution, the outstanding bifunctional electrode (CP-NCP-T || CP-NCP-T) exhibits efficient electrochemical water splitting activity (1.54 V@10 mA cm-2) and outperforms the comparable device Pt/C || IrO2 (1.62 V@10 mA cm-2).

[Effects of plant process on soil organic carbon concentration].

From the viewpoint of the globe and ecosystem, this paper reviewed the effects and the possible action mechanisms of plant process on soil organic carbon concentration. Plant process could affect the source and sink of soil organic carbon, which was likely related with ambient temperature, and forest process could be in favor of the accumulation of soil carbon. Future tasks in this field were put forward to reduce the CO2 concentration in atmosphere through controlling the respiration of soil surface layer and keeping ecosystem balance. It is crucial to make efforts in increasing plant biomass to enhance soil organic carbon storage.

[Impact of land-use change on soil carbon storage].

Through comparing the concentration and inventory of soil organic carbon (SOC) and its distribution in soil profiles under cropland, rangeland, natural secondary forest (brushwood, natural secondary forest dominated by Querces liaotungensis or Populus davidiana) and larch plantations (13, 18 and 25 years old Larix principisrupprechtil), this paper studied the effect of land use change from natural secondary forest to cropland or rangeland as well as from cropland or rangeland to plantation on SOC storage in the Liupan mountain forest zone. The results showed that the concentration of SOC in 0-110 cm soil layer under cropland and rangeland was 54% and 27% lower than that under natural secondary forest, respectively. The difference of SOC concentration between natural secondary forest and cropland or rangeland was greater in 0-50 cm than in 50-110 cm soil layer, while that between larch plantations and cropland or rangeland was greater in 0-40 cm than in 40-110 cm soil layer. The inventory of SOC in 0-110 cm soil layer under cropland and rangeland was respectively 35% and 14% lower than that under natural secondary forest, while 23% lower under cropland and 4% higher under rangeland than that under larch plantations. The difference of SOC inventory between natural secondary forest and cropland or rangeland was greater in 0-50 cm than in 50-110 cm soil layer, while that between plantations and cropland or rangeland was greater in 0-30 cm than in 30-110 cm soil layer. The decreasing magnitude of SOC storage with soil profile depth under natural secondary forest or larch plantations was greater than that under cropland or rangeland. The above-mentioned facts resulted from the changes of SOC input or output and the distribution of roots in soil. The results indicated that the SOC concentration and inventory would decline (mainly in 0-50 cm soil layer) after converting from natural secondary forest to cropland or rangeland, but increase (mainly in 0-30 cm soil layer) following afforestation on cropland. The SOC concentration would increase but its inventory would not change following afforestation on rangeland, and the distribution of the SOC concentration or inventory in soil profile would change with the change of land use in Liupan mountain forest zone.

[The temporal variations of soil respiration under different land use in Liupan Mountain forest zone].

The temporal variations of soil respiration under cropland, rangeland, natural secondary forest (brushwood, nature secondary forest dominated by Querces liaotungensis koiz or Populus davidiana dode) and the plantation of larch (13, 18 and 25-year-old Larix principis-rupprechtil mayr) in Liupan Mountain forest zone was studied. It was found that the rate of soil respiration increased with increasing soil temperature during diurnal variation and the highest temperature was from 13:00 o'clock to 15:00 o'clock, the lowest temperature was from 04:00 o'clock and 08:00 o'clock, the variation of soil respiration rate appeared same trend. The daily rate of soil respiration increased from May to October and which was the highest from August to September and declined on October. The diurnal or seasonal variation of soil respiration rate mainly consisted with the diurnal or seasonal variation of soil temperature and its range under cropland or rangeland was greater than which under forestland (natural secondary forest, plantation or brushwood). The highest rate of soil respiration for diurnal or seasonal variation of soil CO2 efflux under cropland or rangeland was higher than which under the forestland, while the lowest rate of soil respiration under cropland or rangeland was lowered than which under forestland. Annual rate of respiration for natural secondary forest, cropland, rangeland and plantation was 3.96-4.51 t/(hm2.a), 1.91 t/(hm2.a), 5.08 t/(hm2.a) and 4.11-5.55 t/(hm2.a) respectively. The results shows that the diurnal or seasonal variation range of soil respiration rate would increase with conversion from natural forests to cropland or rangeland, while which would decrease following afforestation under cropland or rangeland. In addition, the annual respiration rate would also change with change in land use.