Regulating the electronic structure of metal-organic frameworks via ion-exchanged Ir dispersion for robust overall water splitting.

A facile ion exchange strategy to fabricate CoIrx-BDC with atomically dispersed Ir is developed towards overall water splitting. The optimized CoIr3-BDC requires only 12 and 81 mV to deliver 10 and 100 mA cm-2 alkaline HER, respectively, and only 245 mV to reach 100 mA cm-2 alkaline OER.

Ni dispersed ultrathin carbon nanosheets as bi-functional oxygen electrocatalyst induced from graphite-like porous supramolecule.

Excellent porosity and accessibility are key requirements during carbon-based materials design for energy conversion applications. Herein, a Ni-based porous supramolecular framework with graphite-like morphology (Ni-SOF) was rationally designed as a carbon precursor. Ultrathin carbon nanosheets dispersed with Ni nanoparticles and Ni-Nx sites (Ni@NiNx-N-C) were obtained via in-situ exfoliation during pyrolysis. Due to the hetero-porous structure succeeding from Ni-SOF, the Ni@NiNx-N-C catalyst showed outstanding bifunctional oxygen electrocatalytic activity with a narrow gap of 0.69 V between potential to deliver 10 mA cm-2 oxygen evolution and half-wave potential of oxygen reduction reaction, which even surpassed the Pt/C + IrO2 pair. Therefore, the corresponding zinc-air battery exhibited excellent power output and stability. The multiple Ni-based active sites, the unique 2D structure with a high graphitization degree and large specific surface area synergistically contributed to the excellent bifunctional electrocatalytic activity of Ni@NiNx-N-C. This work provided a novel viewpoint for the development of carbon-based electrocatalyst.

Synthesis of graphene anchored with atomically isolated cobalt from a promising graphite-like supramolecule.

The application of heteroatom-doped graphene for photochemical and electrochemical reactions is primarily hindered by the lack of a controllable and facile synthesis strategy. In this work, few-layer CoN-graphene (1.8 nm thickness) with atomic Co has been fabricated via pyrolysis exfoliation. The half wave potential of CoN-graphene reaches 0.875 V vs. RHE, and the corresponding direct methanol fuel cell performance is 100% (higher than that of the commercial Pt/C catalyst), demonstrating potential for practical application in energy conversion devices.

Soft-template derived Ni/Mo2C hetero-sheet arrays for large current density hydrogen evolution reaction.

Practical structural design and electronic regulation are significant for synthesising efficient electrocatalysts. Therefore, a facile soft-template approach has been applied to successfully grow Ni/Mo2C heterojunction nanosheet arrays on nickel foam (NF) skeleton (NS-Ni/Mo2C@NF) using polyvinylpyrrolidone (PVP) as a soft template. The density functional theory (DFT) calculations reveal that abundant Ni/Mo2C heterojunction in NS-Ni/Mo2C@NF can provide many active sites with a moderate hydrogen adsorption free energy (ΔGH*, 0.037 eV). Benefiting from this nanosheet array structure and abundant Ni/Mo2C heterojunctions, the NS-Ni/Mo2C@NF catalyst can efficiently catalyze HER, especially at large current densities. As a result, only 151 and 271 mV overpotentials are needed to deliver 100 and 1000 mA/cm2 HER, respectively. More importantly, the hydrogen production testing with NS-Ni/Mo2C@NF as the working electrode can run stably for 500 h without activity decay under the current density of 500 mA/cm2 commonly used in industrial water electrolyzers, indicating that NS-Ni/Mo2C@NF has broad application prospects.

Porogen-in-Resin-Induced Fe, N-Doped Interconnected Porous Carbon Sheets as Cathode Catalysts for Proton Exchange Membrane Fuel Cells.

The high dependence of cathodic oxygen reduction reaction on precious Pt catalysts hinders the large-scale commercialization of proton exchange membrane (PEM) fuel cells, while the most promising alternative FeNC catalyst cannot achieve satisfying fuel cell performance yet. By considering the different requirements of atomically dispersed FeNC catalyst on the mass-transfer structure from that of nanoparticle Pt-based catalysts, this work develops a "porogen-in-resin" strategy to approach the Fe, N-doped interconnected porous carbon sheet (ip-FeNCS) catalyst. Three-dimensional (3D) interconnected porous structure and two-dimensional (2D) nanosheet morphology are therefore facilely combined in ip-FeNCS to simultaneously achieve the requirements on the transfer of reactants and accessibility of FeN active sites. Not only great ORR activity can be achieved under both alkaline and acid conditions but also the ip-FeNCS catalyst shows superb activity in practical PEM fuel cells from the high power output to 413 mW/cm2. Such fuel cell performance places this ip-FeNCS catalyst among the best FeNC ORR catalysts reported thus far. This work presents a general and facile approach toward the mass-transfer structure engineering of atomically dispersed carbon catalysts for practical PEM fuel cell applications.