Decoupled electrolysis for hydrogen production and hydrazine oxidation via high-capacity and stable pre-protonated vanadium hexacyanoferrate.

Decoupled electrolysis for hydrogen production with the aid of a redox mediator enables two half-reactions operating at different rates, time, and spaces, which offers great flexibility in operation. Herein, a pre-protonated vanadium hexacyanoferrate (p-VHCF) redox mediator is synthesized. It offers a high reversible specific capacity up to 128 mAh g-1 and long cycling performance of 6000 cycles with capacity retention about 100% at a current density of 10 A g-1 due to the enhanced hydrogen bonding network. By using this mediator, a membrane-free water electrolytic cell is built to achieve decoupled hydrogen and oxygen production. More importantly, a decoupled electrolysis system for hydrogen production and hydrazine oxidation is constructed, which realizes not only separate hydrogen generation but electricity generation through the p-VHCF-N2H4 liquid battery. Therefore, this work enables the flexible energy conversion and storage with hydrogen production driven by solar cell at day-time and electricity output at night-time.

Coupled and collaborative optimization model of impervious surfaces and drainage systems from the flooding mitigation perspective for urban renewal.

Urban pluvial flooding mitigation is a significant challenge in city development. Many mature methods have been used to reduce the risk of flood. The optimal design of impervious surfaces (ODIS) is an adaptive solution to urban flooding from the perspective of urban renewal planning. However, existing ODIS models are limited because they do not consider the drainage systems. To address this issue, this study proposes an elastic and controllable optimization model based on assumptions about rainstorm and drainage capacity, nondominated sorting genetic algorithm-II (NSGA-II), multivariate linear programming (MLP) and soil conservation service curve number model (SCS-CN) in a case study of the old town of Guangzhou city, China. The model not only coupled the drainage systems, but also collaboratively optimized the impervious surfaces and the drainage systems. The results show that the proposed model achieved an optimized efficiency of 5.70 %, which is more than a tenfold improvement compared to existing ODIS models. The study emphasizes that the optimization of the drainage system should be the focus and the optimization of impervious surfaces should be supplementary, and different flood risk areas require different optimization strategies. Furthermore, transforming impervious surfaces into a "high-low-high" spatial distribution of impervious surface densities is the optimal design solution for impervious surfaces. In general, this study offers a novel perspective and approach to urban flooding mitigation, enabling comprehensive control of flooding from a global perspective.

Polypyrrole modification on BiVO4 for photothermal-assisted photoelectrochemical water oxidation.

The bismuth vanadate (BiVO4) photoanode receives extensive attention in photoelectrochemical (PEC) water splitting. However, the high charge recombination rate, low electronic conductivity, and sluggish electrode kinetics have inhibited the PEC performance. Increasing the reaction temperature for water oxidation is an effective way to enhance the carrier kinetics of BiVO4. Herein, a polypyrrole (PPy) layer was coated on the BiVO4 film. The PPy layer could harvest the near-infrared light to elevate the temperature of the BiVO4 photoelectrode and further improve charge separation and injection efficiencies. In addition, the conductive polymer PPy layer acted as an effective charge transfer channel to facilitate photogenerated holes moving from BiVO4 to the electrode/electrolyte interface. Therefore, PPy modification led to a significantly improved water oxidation property. After loading the cobalt-phosphate co-catalyst, the photocurrent density reached 3.64 mA cm-2 at 1.23 V vs the reversible hydrogen electrode, corresponding to an incident photon-to-current conversion efficiency of 63% at 430 nm. This work provided an effective strategy for designing a photothermal material assisted photoelectrode for efficient water splitting.

Decoupled Water Electrolysis Driven by 1†cm2 Single Perovskite Solar Cell Yielding a Solar-to-Hydrogen Efficiency of 14.4 .

Invited for this month's cover is the group of Yubin Chen at Xi'an Jiaotong University as well as collaborators at Shanghai Jiao Tong University. The image shows a decoupled water electrolysis system driven by a single perovskite solar cell (PSC) to produce separated hydrogen and oxygen. The Research Article itself is available at 10.1002/cssc.202201689.

Decoupled Water Electrolysis Driven by 1 cm2 Single Perovskite Solar Cell Yielding a Solar-to-Hydrogen Efficiency of 14.4 .

Solar water splitting by photovoltaic (PV) electrolysis is a promising route for sustainable hydrogen production. However, multiple PV cells connected in series are generally required to fulfil the practical electrolytic voltages, which inevitably increases the system complexity and resistance. Decoupled water electrolysis for separate hydrogen and oxygen evolution needs smaller voltage to drive each half-reaction, which provides a feasibility to achieve the single PV cell driven water electrolysis. Herein, by introducing sodium nickelhexacyanoferrate (NaNiHCF) as the redox mediator, decoupled acid water electrolyzer and amphoteric water electrolyzer were respectively constructed. The required voltages for the hydrogen or oxygen evolution steps matched with the output voltages of the perovskite solar cell (PSC). Impressively, by combining one 1 cm2 FAPbI3 -based PSC (efficiency: 18.77 %) with the decoupled amphoteric water electrolyzer, a solar-to-hydrogen (STH) efficiency of 14.4 % was achieved, which outperformed previously reported PSC-driven water electrolysis cells.