Oxygen Evolution Reaction Bifunctional Electrocatalysts Research Articles

Hollow Ti3C2Tx MXene sphere-based ZIF-67 derived central radiative cobalt-tipped carbon nanotubes electrocatalysts for ORR and OER

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a key role in many renewable energy conversion and storage technologies. As the state-of-the-art ORR and OER electrocatalysts, noble-metal-based electrocatalysts suffer from high price, low earth abundance, single functionality, and poor stability. Developing high performance noble-metal-free ORR and OER bifunctional electrocatalysts as alternatives is highly desirable but remains a significant challenge. In this work, we reported a metal-organic-framework-engaged strategy for the fabrication of central radiative cobalt-tipped N-doped carbon nanotube/hollow Ti3C2Tx sphere composites (h-Ti3C2Tx@Co-NCNT), in which ZIF-67 particles were in situ grown on spherical structure composed of Ti3C2Tx nanosheets constructed with hard template PMMA and then were converted to cobalt-tipped N-doped carbon nanotubes through a pyrolysis process. The hollow Ti3C2Tx nanosheets sphere not only served as conductive scaffolds for the growth of Co-NCNT but also balanced the tradeoff between graphitization of carbon and the surface area. Benefiting from the abundant Co-N/C active sites, reasonably high graphitization of carbon and suitable surface areas, the optimized h-Ti3C2Tx@Co-NCNT manifested comparable ORR (half-wave potential of 0.843 V) and OER (overpotential of 323 mV) activities. In addition, the h-Ti3C2Tx@Co-NCNT assembled zinc-air battery exhibits superior performance beyond commercial Pt/C+RuO2. Certificating this strategy can provide great opportunity for its application in renewable conversion and storage technologies.

NiSe-modified CoMoO4 nanosheets as bifunctional electrocatalysts for hydrogen and oxygen evolution reactions

Selecting self-supporting substrates with large specific surface areas is an effective strategy to avoid the agglomeration of nanomaterials and improve the structural stability of materials while increasing their electrical conductivity. In this study, CoMoO4 nanosheet structures were first grown on a nickel foam (NF) substrate by hydrothermal and calcination processes. Then, NiSe nanoparticles were deposited on NF/CoMoO4 by a constant potential method to construct NF/CoMoO4 @NiSe nanosheet electrode materials with graded layered structures. This nanosheet structure grown on NF substrates provided enough space for mass transfer and fully exposed the electrochemical active sites. Meanwhile, the self-supported electrode reduced the indirect contact resistance between the electrocatalyst and the substrate, which promoted the timely release of generated bubbles from the electrode. The NF/CoMoO4 @NiSe electrode exhibited excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic activities under alkaline conditions. Overpotentials of only 58 mV and 184 mV were needed to achieve a current density of 10 mA·cm−2 for the HER and OER, respectively. This study presents new ideas for the construction of nanosheet structures and the design of efficient HER and OER bifunctional electrocatalysts using transition metal selenides.

Synthesis of MgNiO2/CoNC-Based Ternary Metallic Dual-Active Interfacial Porous Hollow Nanocages as Efficient Oxygen Reduction Reaction and Oxygen Evolution Reaction Bi-Functional Electrocatalysts

Combining the catalytic activities of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) into one electrocatalyst is of great significance in simultaneously prompting the charge-discharge cycles of various renewable energy storage and conversion systems such as metal-air batteries. Herein we report a ternary metallic based MgNiO2/CoNC porous hollow nanocage composite, which assembled with intimate contacted MgNiO2 and Co species to form the ultrathin nanocage shells and serve as the ORR and OER active components respectively to reveal a highly bi-functional catalytic performance. The possible synergy of each seamlessly connected metallic sites renders the hybrid material with excellent ORR and OER activities, which outperform than the corresponding benchmarks. Particularly, we speculate such efficient catalytic activity might arise from the synergistic chemical coupling effects within MgNiO2/CoNC and therefore, these results reveals promising prospects in developing multi-metallic composites toward efficient electrochemical energy devices.

Recent progress on earth abundant hydrogen evolution reaction and oxygen evolution reaction bifunctional electrocatalyst for overall water splitting in alkaline media

Abstract Electrochemical water-splitting is one of the promising ways for producing clean chemical fuel (Hydrogen) while cheap-earth-abundant-bifunctional-electrocatalyst is one of the possible way for improving the overall cost efficiency of water-splitting. This paper reviews the chemical state, hydrogen and oxygen evolution reaction activity in alkaline media, overall water-splitting performance in alkaline media, stability, and possible-factors for improving its efficiency of various kinds of recently reported electrocatalyst such as Ni-P, Co-P, Ni-Co-P, graphene-Co-P, O/N/C-Co/Ni, Ni-S, B-Ni/Co, Ni-Co, Mo, Se, Fe, Mn/Zn/Ti, and metal-free based earth-abundant-bifunctional-electrocatalyst. This paper also reviews and highlights the remarkable water splitting performance of the earth-abundant-bifunctional-electrocatalyst those exhibit better or well comparable with Pt/C//RuO2.