The critical prerequisite for realizing the industrial application of photocatalytic technology lies on developing efficient photocatalyst through reasonable and large-scale modification strategy. Herein, the rapid and solvent-free high-energy ball-milling procedure was adopted to modify graphitic carbon nitride (g-C3N4) on a large-scale by phosphorus (P) atom doping and molybdenum phosphide (MoP) decorating. It is confirmed that P doping can introduce a mid-gap state in the band gap of g-C3N4, broadening the light responsive region and enhancing the electrical conductivity of g-C3N4. The Mo N bond at the interface of P-doped g-C3N4 and MoP acting as electrons “delivery channels” facilitates the charge transfer from P-doped g-C3N4 to MoP, while the Schottky barrier promotes the separation of photocarriers. As a result, the optimized P-doped g-C3N4/MoP photocatalyst performs an improved H2 evolution rate of 4917.83 μmol·g−1·h−1 and a favorable H2 production stability. This work offers a replicable prototype on adopting high-energy ball-milling to modify photocatalyst.

High-Energy Ball-Milling Constructing P-doped g-C3N4/MoP Heterojunction with Mo-N bond bridged Interface and Schottky barrier for Enhanced Photocatalytic H2 Evolution

Engineering iron-group bimetallic nanotubes as efficient bifunctional oxygen electrocatalysts for flexible Zn–air batteries

Manganese-incorporated Co3O4 catalysts were prepared via thermal pyrolysis of ZIF-67, and the effect of manganese incorporation and annealing temperature on their catalytic performances for oxygen reduction and evolution reactions (ORR, OER) were investigated. Notable crystalline distortion was induced by manganese insertion into Co3O4 lattice, resulting in smaller crystallite size, more abundant Co2+ and considerable oxygen vacancies. All these properties were regarded as the crucial origins for electrocatalytic activity elevation. The catalyst annealed at 450 °C (denoted as Mn/Co-450) exhibited the optimal catalytic activity with an ultra-low potential gap (0.83 V). Using Mn/Co-450 as an air cathode, the zinc-air battery delivered high power density (115.5 mW cm−2), competitive specific capacity (783.4 mAh g−1) and good cycling stability. The theoretical overpotentials of ORR and OER were respectively decreased by 0.18 V and 0.05 V by DFT calculation due to the weakened interaction between Co and OH group and the strengthened Co-OOH interaction. 

Mn-incorporated Co3O4 bifunctional electrocatalysts for zinc-air battery application: An experimental and DFT study

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.

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

Electrochemical energy conversion and storage through hydrogen has revolutionized sustainable energy systems using fuel cells and electrolyzers. Regrettably, the sluggish alkaline hydrogen oxidation reaction (HOR) hampers advances in fuel cells. Herein, we report a Pt/Ni3N-Mo2C bifunctional electrocatalyst toward HOR and hydrogen evolution reaction (HER). The Pt/Ni3N-Mo2C exhibits remarkable HOR/HER performance in alkaline media. The mass activity at 50 mV and exchange current density of HOR are 5.1 and 1.5 times that of commercial Pt/C, respectively. Moreover, it possesses an impressive HER activity with an overpotential of 11 mV @ 10 mA cm-2, which is lower than that of Pt/C and most reported electrocatalysts under the same conditions. Density functional theory (DFT) calculations combined with experimental results reveal that Pt/Ni3N-Mo2C not only possesses an optimal balance between hydrogen binding energy (HBE) and OH- adsorption but also facilitates water adsorption and dissociation on the catalyst surface, which contribute to the excellent HOR/HER performance. Thus, this work may guide bifunctional HOR/HER catalyst design in the conversion and transport of energy.

Electronic Modulation of Pt Nanoparticles on Ni3N-Mo2C by Support-Induced Strategy for Accelerating Hydrogen Oxidation and Evolution.

Developing high-efficient non-noble metal-based catalysts for oxygen reduction reaction (ORR) is an inevitable way to improve Zinc-air batteries' performance (ZAB). Herein, we report a Cu3P/MoP electrocatalyst (Cu3P/MoP@C) supported by hollow-porous-carbon nanospheres displaying high electrocatalytic activity and exceptional durability in alkaline media. The optimized ORR catalyst outperformed the benchmark Pt/C (20 wt%) and most recently reported Cu-/Mo-based catalysts in various aspects. X-ray photoelectron spectroscopy reveals that the excellent ORR performance originates from the charge transfer between of Cu3P and MoP species. Besides, the large specific surface area of Cu3P/MoP@C with mesoporous structure is particularly advantageous for the inner surface contact with electrolyte to accelerate ORR kinetics. Moreover, Cu3P/MoP@C also exhibits a large power density of 156 mW cm−2, a high round-trip efficiency, and superb stability over 231 h superior to Pt/C in the ZAB. This work offers a scalable and promising approach for the rational fabrication of hollow porous structure materials.

Electronic/mass transport increased hollow porous Cu3P/MoP nanospheres with strong electronic interaction for promoting oxygen reduction in Zn-air batteries

The high‐efficiency multifunctional materials have considerable significance in the area of sustainable energy to developing a cross‐usable and low‐cost catalyst. Nevertheless, substantial challenges are ahead on designing and synthesizing a high performance in a scalable and straightforward manner. Here, we have developed a novel bifunctional catalyst based on Ru/CoP nanoboxes (NBs) prepared using ZIF‐67 as a precursor. The nano hollow box structure and the strong electronic interaction between Ru clusters and CoP component are confirmed. The Ru/CoP NBs as a catalyst show excellent activities for catalytic NaBH4 hydrolysis such as high turnover frequency (1202.2 min−1), and small electrocatalytic H2 evolution overpotential (49 mV@10 mA cm−2) under ambient conditions. Besides, Ru/CoP NBs also display good stability and reusability. The excellent catalytic performance of Ru/CoP NBs is attributed to the synergy between Ru clusters and CoP species as well as the unique morphology that accelerates charge transfer, provides higher active surface area, and facilitates solute transport and gas emission.

Well-Dispersed Ru-Clusters Decorating Nanobox-Structured CoP Synergistically Catalyze the NaBH4 Hydrolysis and Electro-Reductive H2 Evolution

Engineering cobalt nitride nanosheet arrays with rich nitrogen defects as a bifunctional robust oxygen electrocatalyst in rechargeable Zn-air batteries.

Chuan Hu

Papers

Electronic/mass transport increased hollow porous Cu3P/MoP nanospheres with strong electronic interaction for promoting oxygen reduction in Zn-air batteries

Well-Dispersed Ru-Clusters Decorating Nanobox-Structured CoP Synergistically Catalyze the NaBH4 Hydrolysis and Electro-Reductive H2 Evolution

Engineering cobalt nitride nanosheet arrays with rich nitrogen defects as a bifunctional robust oxygen electrocatalyst in rechargeable Zn-air batteries.