Heping Yu

Bio: Heping Yu is an academic researcher from Qingdao University. The author has contributed to research in topics: Catalysis & Self-healing hydrogels. The author has an hindex of 1, co-authored 3 publications receiving 1 citations.

Study on the Simple Surface Treatments of N, P Dual-doped Carbon as Metal-free Catalyst for Metal-air Batteries

Abstract: N, P dual‐doped porous carbon with high specific surface area of ∼2000 m2 g−1 was prepared via foaming‐carbonization process. It was demonstrated that the simple surface treatment and modification can conveniently further improve the catalytic performance of oxygen reduction reaction (ORR). The results showed that chemisorbed phosphorus can promote the surface treatment of sodium borohydride (NaBH4). The modified novel sites, adsorbing water molecules of a semi‐free state, promoted the offensive key steps of H2O molecules in ORR. After post‐treatment, the limit current density increased from 5.0 to 6.1 mA cm−2 with a decreased Tafel slope and the onset potential positively shifted. This surface‐modified catalyst was applied to Zn‐air battery and Al‐air battery, and had exhibited good applicability and excellent performances. This work illustrates that the simple post‐treatments can conveniently and effectively improve the ORR performance of metal‐free carbon catalysts.

FeNiP nanoparticle/N,P dual-doped carbon composite as a trifunctional catalyst towards high-performance zinc-air batteries and overall water electrolysis.

Abstract: A composite catalyst with a novel construction of bimetallic phosphide FeNiP nanoparticles embedded in an N,P double-doped carbon matrix was prepared. It was demonstrated to be a trifunctional catalyst that can efficiently catalyze the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It was found that the introduction of oleylamine during the preparation can adjust the catalytic sites and finally lead to ideal catalytic performances. The obtained catalyst exhibited efficient ORR catalytic performance that surpassed the commercial Pt/C catalyst, with the OER performance comparable to that of RuO2 as well as excellent HER performance. The ORR half-wave potential is 0.879 V (vs. RHE) in 0.1 M KOH solution, while the OER overpotential at a current density of 10 mA cm−2 is only 280 mV in 1 M KOH solution. The potential gap between the ORR and OER was only 0.700 V in 0.1 M KOH solution. This trifunctional catalyst was further evaluated in energy devices including zinc–air batteries and water electrolysis. The liquid zinc–air battery assembly achieved a power density of 169 mW cm−2 and stably undergoes charge–discharge cycles for 210 hours. The solid-state zinc–air battery achieved a power density of 70 mW cm−2 and stably undergoes charge–discharge cycles for 40 hours. These performances surpassed the batteries assembled with a Pt/C-RuO2 mixed catalyst. This work established a foundation of composite catalysts coupled with bimetallic phosphide and hybrid carbon substrates, which will promote the development of high-performance multifunctional catalysts and their application in energy devices.

Preparation and Properties of Double-Crosslinked Hydroxyapatite Composite Hydrogels

Abstract: Natural polymer hydrogels have good mechanical properties and biocompatibility. This study designed hydroxyapatite-enhanced photo-oxidized double-crosslinked hydrogels. Hyaluronic acid (HA) and gelatin (Gel) were modified with methacrylate anhydride. The catechin group was further introduced into the HA chain inspired by the adhesion chemistry of marine mussels. Hence, the double-crosslinked hydrogel (HG) was formed by the photo-crosslinking of double bonds and the oxidative-crosslinking of catechins. Moreover, hydroxyapatite was introduced into HG to form hydroxyapatite-enhanced hydrogels (HGH). The results indicate that, with an increase in crosslinking network density, the stiffness of hydrogels became higher; these hydrogels have more of a compact pore structure, their anti-degradation property is improved, and swelling property is reduced. The introduction of hydroxyapatite greatly improved the mechanical properties of hydrogels, but there is no change in the stability and crosslinking network structure of hydrogels. These inorganic phase-enhanced hydrogels were expected to be applied to tissue engineering scaffolds.

Preparation and characterization of photo-oxidative dual-crosslinked chitosan/hyaluronic acid hydrogels

Abstract: Here, photo-crosslinked CM/HM hydrogels and photo-oxidative dual-crosslinked CM/HM/CSD hydrogels (DH) were fabricated based on chitosan methacrylate (CM), aminoethyl methacrylated hyaluronic acid (HM) and chitosan-3,4-dihydroxybenzaldehyde (CSD). Two kinds of different substitution degree of CM and HM and one kind of CSD were prepared respectively by amidation. The chemical structures of CM, HM, CSD were determined using proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy, fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV–vis) spectrum and differential scanning calorimetry (DSC). CM/HM hydrogels and DH with adjustable properties were obtained by adjusting the degree of substitution (DS) and the type of network. These hydrogels can be easily and quickly gelled in situ and all hydrogels had desirable swelling percentages and biodegradability. Furthermore, introduction of catechins enhanced the mechanical strength of hydrogels meanwhile improved the flexibility, and maintained the pore structure. These controllable hydrogels have great potential for tissue engineering applications. • Two kinds of hydrogels were formed via photo- and oxidative-crosslinking. • Easily and quickly gelled in situ. • The degree of substitution adjusted the properties of photo-crosslinked hydrogels. • Secondary covalent network formed by catechol improved the toughness.

Controllable Solid-Phase Fabrication of an Fe2O3/Fe5C2/Fe-N-C Electrocatalyst toward Optimizing the Oxygen Reduction Reaction in Zinc-Air Batteries.

Abstract: Preparing advanced electrocatalysts via solid-phase reactions encounters the challenge of low controllability for multiconstituent hybridization and microstructure modulation. Herein, a hydrothermal-mimicking solid-phase system is established to fabricate novel Fe2O3/Fe5C2/Fe-N-C composites consisting of Fe2O3/Fe5C2 nanoparticles and Fe,N-doped carbon species with varying morphologies. The evolution mechanism featuring a competitive growth of different carbon sources in a closed hypoxic space is elucidated for a series of Fe2O3/Fe5C2/Fe-N-C composites. The size and dispersity of Fe2O3/Fe5C2 nanoparticles, the graphitization degree of the carbonaceous matrix, and their diverse hybridization states lead to disparate electrocatalytic behaviors for the oxygen reduction reaction (ORR). Among them, microspherical Fe2O3/Fe5C2/Fe-N-C-3 exhibits an optimal ORR performance and the as-assembled zinc-air battery shows all-round superiority to the Pt/C counterpart. This work presents a mild solid-phase fabrication technique for obtaining a variety of nanocomposites with effective control over composition hybridization and microstructural modulation, which is significantly important for the design and optimization of advanced electrocatalysts.

Material design and surface chemistry for advanced rechargeable zinc–air batteries

Abstract: Zinc–air batteries (ZABs) have been considered as a next-generation battery system with high energy density and abundant resources. However, the sluggish multi-step reaction of the oxygen is the main obstacle for the practical application of ZABs. Therefore, bifunctional electrocatalysts with high stability and activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are greatly required to promote the catalytic reaction. In this review, we first explain the reaction mechanism of the ZABs, mainly focusing on multiple oxygen intermediates. Then, the latest studies on bifunctional electrocatalysts for the air cathodes and their progress of the ZABs are discussed with following aspects: platinum group metal, metal-free, transition metal, and metal compound-derived electrocatalysts. Finally, we highlight the advanced ZAB systems with the design of the full-temperature range operation, the all-solid-state, and the newly reported non-alkaline electrolyte, summarizing the remaining challenges and requirements of the future research directions.

Self-Supported FeNiP Nanosheet Arrays as a Robust Bifunctional Electrocatalyst for Water Splitting

Abstract: Bimetallic FeNiP nanosheet arrays on a nickel foam (FeNiP@NFO) are fabricated by an in situ oxidative etching process coupled with phosphorization. The self-supported FeNiP@NFO catalyst exhibits prominent catalytic activity for a hydrogen evolution reaction with overpotentials as low as 64, 82, and 54 mV at 10 mA·cm–2 in 1.0 M PBS, 1.0 M KOH, and 0.5 M H2SO4, respectively, surpassing most reported non-noble catalysts. Moreover, FeNiP@NFO requires an overpotential of 193 mV in 1.0 M KOH to drive 10 mA·cm–2 for an oxygen evolution reaction. The overall water-splitting electrolyzer assembled with FeNiP@NFO as both the anodic and cathodic electrodes exhibits an extremely low cell voltage of 1.49 V to achieve a current density of 10 mA·cm–2, which is much lower than that of most alkaline electrolysis systems. The extraordinary electrocatalytic activity of FeNiP@NFO is ascribed to the synergistic effect between elements and the special network compiled by nanosheet arrays, which offers high conductivity, abundant accessible active sites, easy hydrogen release channels, and fast electron transportation.

Hypercrosslinked polymer-mediated fabrication of binary metal phosphide decorated spherical carbon as an efficient and durable bifunctional electrocatalyst for rechargeable Zn-air batteries.

Abstract: Bifunctional oxygen catalysts with excellent catalytic activity and durability towards both oxygen reduction and oxygen evolution reactions (ORR/OER) are pivotal for long-term rechargeable Zn-air batteries. Herein, we report a spherical carbon decorated with FeP and CoP nanoparticles (denoted as FeCoP/NPC) as an ORR/OER bifunctional electrocatalyst for rechargeable Zn-air batteries. HCTCz@Fe/Co-PA is first produced by the modification of phytic acid (PA) onto (into) a porous cross-linked polymeric sphere of poly(bis(N-carbazolyl)-1,2,4,5-tetrazine) (HCTCz), followed by chelating with metal ions (i.e., Fe3+ and Co2+). The subsequent pyrolysis yields FeCoP/NPC, which shows prominent activity and reliability for the ORR and OER due primarily to the synergistic effect of FeP and CoP active sites and N/P co-doped carbon. The aqueous Zn-air battery assembled with FeCoP/NPC provides high specific capacity and peak power density. Notably, the constructed Zn-air battery can be repetitively charged and discharged for 1200 h at 5 mA cm-2. In addition, a flexible solid-state Zn-air battery made from FeCoP/NPC exhibits a power density of 74 mW cm-2 and repeatedly works for 90 h at 2 mA cm-2. This work opens up an avenue for the preparation of highly efficient bifunctional electrocatalysts for Zn-air batteries considering the extensive N-rich polymer precursors and various metal phosphide nanoparticles.