Synergistic coupling of IrNi/Ni(OH)2nanosheets with polypyrrole and iron oxyhydroxide layers for efficient electrochemical overall water splitting.

The design of electrocatalysts with excellent activity and stability for overall water splitting is highly desirable, and remains a challenge. Constructing heterojunctions onto the same substrate is beneficial for the integration of a water-splitting reaction. Herein, self-supported IrNi/Ni(OH)2@PPy and IrNi/Ni(OH)2@FeOOH are fabricated by coupling polypyrrole (PPy) and iron oxyhydroxide (FeOOH) on IrNi/Ni(OH)2nanosheets array, respectively. Benefiting from the nanosheet structure, composition, and heterogeneous interface, the as-constructed IrNi/Ni(OH)2@PPy and IrNi/Ni(OH)2@FeOOH catalysts can efficiently drive the hydrogen evolution reaction and oxygen evolution reaction, respectively. Moreover, the electrolyzer consisting of IrNi/Ni(OH)2@PPy and IrNi/Ni(OH)2@FeOOH for water splitting requires only a low cell voltage of 1.49 V to deliver 10 mA cm-2. This study provides a useful strategy for constructing efficient electrocatalysts by synergistic composition modulation and interface engineering.

Modulating Coordination of Iron Atom Clusters on N,P,S Triply-Doped Hollow Carbon Support towards Enhanced Electrocatalytic Oxygen Reduction.

Constructing atom-clusters (ACs) with in situ modulation of coordination environment and simultaneously hollowing carbon support are critical yet challenging for improving electrocatalytic efficiency of atomically dispersed catalysts (ADCs). Herein, a general diffusion-controlled strategy based on spatial confining and Kirkendall effect is proposed to construct metallic ACs in N,P,S triply-doped hollow carbon matrix (MACs /NPS-HC, M=Mn, Fe, Co, Ni, Cu). Thereinto, FeACs /NPS-HC with the best catalytic activity for oxygen reduction reaction (ORR) is thoroughly investigated. Unlike the benchmark sample of symmetrical N-surrounded iron single-atoms in N-doped carbon (FeSAs /N-C), FeACs /NPS-HC comprises bi-/tri-atomic Fe centers with engineered S/N coordination. Theoretical calculation reveals that proper Fe gathering and coordination modulation could mildly delocalize the electron distribution and optimize the free energy pathways of ORR. In addition, the triple doping and hollow structure of carbon matrix could further regulate the local environment and allow sufficient exposure of active sites, resulting in more enhanced ORR kinetics on FeACs /NPS-HC. The zinc-air battery assembled with FeACs /NPS-HC as cathodic catalyst exhibits all-round superiority to Pt/C and most Fe-based ADCs. This work provides an exemplary method for establishing atomic-cluster catalysts with engineered S-dominated coordination and hollowed carbon matrix, which paves a new avenue for the fabrication and optimization of advanced ADCs.

A CTAB-mediated antisolvent vapor route to shale-like Cs4PbBr6 microplates showing an eminent photoluminescence.

Compared with nanoscale quantum dots (QDs), the large-sized perovskite crystals not only possess better stability but also are convenient for application exploration. Herein, we develop a facile and efficient antisolvent vapor-assisted recrystallization approach for the synthesis of large-sized Cs4PbBr6 perovskite crystal microplates. In this method, for the first time, the shale-like Cs4PbBr6 microplates with lateral dimensions of hundreds of microns are fabricated by employing cetyltriethylammnonium bromide (CTAB) as a morphology-directing agent. FESEM, TEM, and AFM characterizations indicate that the as-obtained shale-like Cs4PbBr6 microplates are actually formed by 6-8 nm thick Cs4PbBr6 nanosheets with orientational stacking. Importantly, such highly crystalline Cs4PbBr6 microplates with shale-like morphology exhibit a narrow and intense green PL emission with a 59% PL quantum yield. Moreover, the planar structure of shale-like Cs4PbBr6 microplates makes it easy to form a preferred orientation on a substrate, which endow them with promising potential in optoelectronic devices such as lighting and displays.