Alkaline electrochemical water oxidation powered by renewable energies is a promising and environmentally friendly way to produce hydrogen. The industrial water electrolyzers are commonly operated at a high current density, calling for abundant and durable active sites to participate in. The rational design of hierarchically structured electrocatalysts is thus essential to industrial water electrolyzers. Herein, we develop a Fe³⁺ induced nanosizing strategy for fabricating such a hierarchical FeCo LDH@Co₃O₄ (LDH: layered double hydroxide) nanostructure array for high-rate water oxidation. Density functional theory (DFT) simulations indicate that the introduction of Fe³⁺ with a small ion radius and high electrical repulsion in the LDH layer distorted the LDH layer, resulting in a reduced nanosheet size and enabling the formation of a hierarchical structure. Such structure cannot be achieved without the participation of Fe³⁺ cations. Benefiting from the significantly enhanced electrochemical surface areas and charge/mass transport due to the hierarchical structure together with the boosted intrinsic activity by electronic modulation of Fe³⁺, such FeCo LDH@Co₃O₄ electrode can deliver an industrial-level current density of 1,000 mA·cm⁻² at a small overpotential of 392 mV for water oxidation. When assembled in a water electrolyzer, it delivers a current density of 100 mA·cm⁻² at a low operation voltage of 1.61 V. Powered by solar light, the electrolyzer demonstrates high solar-to-hydrogen efficiency of 18.15% with stable and reproducible photoresponse. These results provide new insights for constructing hierarchical nanostructures for advanced water oxidation and other diverse applications.

High-performance supercapacitors require electrodes featuring a high surface area, suitable porosity, and conductivity. Metal-organic frameworks (MOFs) hold a high surface area and suitable porosity while insufficient conductivity. Herein, a single-step chemical strategy was developed to directly synthesize a composite of copper-nickel rubeanate MOF and highly conductive reduced graphene oxide (rGO) nanosheets (CNRG-MOF) on nickel foam (CNRG-MOF/NF) electrode. The nanocomposite enables it to use as a high-performance supercapacitor electrode. The bimetallic CNRG-MOF/NF electrode exhibits superior electrochemical performance than its single metallic counterparts. The optimized CNRG-MOF/NF electrode represents a high specific capacitance of 846.15 F g⁻¹ at a current density of 1.0 A g⁻¹. A three-electrode system exhibited up to 96.37 % capacitance retention after 7000 galvanostatic charge-discharge (GCD) cycles, indicating its excellent stability. These results may pave the way for the direct use of MOF materials for electrochemical energy devices instead of pyrolyzing the MOFs to improve the conductivity while losing controllable structural merits. GCD curve was obtained at different current densities to evaluate the nanocomposite's asymmetric setup charge storage capability. The electrode capacity for the asymmetric system was measured as 93.3 F g⁻¹, which proves the capacitive property of CNRG-MOF/NF electrode.

The electrochemical nitrogen reduction reaction (NRR) as an energy-efficient approach for ammonia synthesis is hampered by the low ammonia yield and ambiguous reaction mechanism. Herein, phosphorus-doped carbon nanotube (P-CNTs) is developed as an efficient metal-free electrocatalyst for NRR with a remarkable NH₃ yield of 24.4 μg·h^-1·mg^-1_cat. and partial current density of 0.61 mA·cm^-2. Such superior activity is found to be from P doping and highly conjugated CNTs substrate. Experimental and theoretical investigations discover that the electron-deficient phosphorus sites with Lewis acidity should be genuine active sites and NRR on P-CNTs follows the distal pathway. These findings provide insightful understanding on NRR processes on P-CNTs, opening up opportunities for the rational design of highly-active cost-effective metal-free catalysts for electrochemical ammonia synthesis.

The development of new non-precious metal catalysts and understanding the origin of their activity for the hydrogen evolution reaction (HER) are essential for rationally designing highly active low-cost catalysts as alternatives to state-of-the-art precious metal catalysts. Herein, manganese oxide/hydroxide was demonstrated as a highly active electrocatalysts for the HER by fabricating MnO₂ nanosheets coated with Cu₂O nanowire arrays (Cu₂O@MnO₂ NW@NS) on Cu foam followed by an in situ chronopotentiometry (CP) treatment. It was discovered that the in situ transformation of Cu₂O@MnO₂ into Cu@Mn(OH)₂ NW@NS by the CP treatment drastically boosted the catalytic activity for the HER due to an enhancement of its intrinsic activity. Together with the benefits from such three-dimensional (3D) core–shell arrays for exposing more accessible active sites and efficient mass and electron transfers, the resulting Cu@Mn(OH)₂ NW@NS exhibited excellent HER activity and outstanding durability in terms of a low overpotential of 132 mV vs. RHE at 10 mA/cm². Overall, we expect these findings to generate new opportunities for the exploration of other Mn-based nanomaterials as efficient electrocatalysts and enable further understanding of their catalytic processes.

Organolead halide perovskite solar cells have achieved a certified power-conversion efficiency (PCE) of 22.1% and are thus among the most promising candidates for next-generation photovoltaic devices. To date, most high-efficiency perovskite solar cells have employed arylamine-based hole-transport materials (HTMs), which are expensive and have a low mobility. The complicated doping procedures and the potentially stability-adverse dopants used in these HTMs are among the major bottlenecks for the commercialization of perovskite solar cells (PSCs). Herein, we present a polythiophene-based copolymer (PDVT-10) with a hole mobility up to 8.2 cm²·V^-1·s^-1 and a highest occupied molecular orbital level of -5.28 eV as a hole-transport layer (HTL) for a PSC. A device based on this new HTM exhibited a high PCE of 13.4% under 100 mW·cm^-2 illumination, which is one of the highest PCEs reported for the dopant-free polymer-based HTLs. Moreover, PDVT-10 exhibited good solution processability, decent air stability, and thermal stability, making it a promising candidate as an HTM for PSCs.