Single-atom catalysts cathode for lithium-Oxygen batteries：A review

Recently, single-atom catalysts (SACs) have been found to be one of the promising candidates for oxygen electrocatalysis in rechargeable lithium-oxygen batteries (LOBs), owing to their high oxygen electrocatalytic activity and high stability originated from their unique coordination environments and electronic properties. As a new type of catalysts for LOBs, the advancements have never been reviewed and discussed comprehensively. Herein, the breakthroughs in the design of various types of SACs as the cathode catalysts for LOBs are summarized, including Co-based, Ru-based, and other types of SACs. Moreover, considerable emphasis is placed on the correlations between the structural feature of the SAC active sites and the electrocatalytic performance of LOBs. Finally, perspective and challenges of SACs for practical LOBs are also provided. This review could provide an intensive understanding of SACs for designing efficient oxygen electrocatalysis and offers a useful guideline for the development of SACs in the field of LOBs.

Improving the Performance of Microbial Fuel Cells with Modified Carbon Aerogel Based Cathode Catalysts

Microbial fuel cells (MFCs) are capable of converting the chemical energy of biodegradable organic matter directly into electricity, thus they can be applied in various fields: waste elimination, biosensor industry and production of renewable energy. In this study, the efficiency of noble metal free carbon aerogel based cathode catalysts was investigated and compared to plain glassy carbon cloth without catalyst (CC ) and platinum containing carbon powder catalyst ( PtC ) in H-type MFCs. Surface extension by carbon aerogel (CA ) enhanced the maximum power density by 34 % compared to CC, to 14.1 W m−3. With nitrogen doped carbon aerogel (NCA) the performance was further increased to 15.7 W m−3. Co-doping the resorcinol-melamine-formaldehyde based aerogel with graphene oxide (GNCA) resulted in an additional power increase of 70 %, indicating that the electrocatalytic activity of NCAs can be considerably improved by co-doping with graphene oxide. Although the performance of GNCA remained below that of PtC (50.2 W m−3) in our investigations, it can be concluded that GNCA based coatings may provide a noble metal free, and therefore competitive and sustainable alternatives for cathode catalysis in MFC based technologies.

On the Correlation between the Oxygen in Hydrogen Content and the Catalytic Activity of Cathode Catalysts in PEM Water Electrolysis

Altogether five platinum group metal (PGM) and PGM-free cathode catalysts were investigated in full PEM water electrolysis cells regarding their polarisation behaviour and their hydrogen and oxygen recombination properties. It was shown that the recombination activity of permeated oxygen and evolved hydrogen within the cathodic catalyst layer correlates with the activity of the oxygen reduction reaction (ORR) which was determined ex situ with linear sweep voltammetry. We found that the investigated PGM-free cathode catalysts had a low activity for the ORR resulting in higher measurable oxygen in hydrogen volume fractions compared to the PGM catalysts, which are more active for the ORR. Out of the three investigated PGM-free catalysts, only one commercially available material based on a Ti suboxide showed a similar good polarisation behaviour as the state of the art cathode catalyst platinum, while its recombination activity was the lowest of all catalysts. In addition to the recombination of hydrogen and oxygen on the electrocatalysts, we found that the prevalent carbon-based cathodic porous transport layers (PTL) also offer catalytically active recombination sites. In comparison to an inactive PTL, the measurable oxygen flux using carbon-based PTLs was lower and the recombination was enhanced by microporous coatings with high surface areas.

Review on bimetallic catalysts for electrocatalytic denitrification

Accelerated industrialization disrupts the global nitrogen cycle, resulting in alarmingly increased nitrate in groundwater and other water bodies. Electrocatalytic nitrate reduction (NO3RR) with high automation can effectively remove nitrate from polluted water, thus avoiding nitrate accumulation. However, the sluggish cathode reaction kinetics severely hampered the efficiency of NO3RR. Developing high-performance cathode catalysts is of great significance for boosting NO3RR. Compared with pure metal catalysts, bimetal catalysts can further improve the cathode activity and selectivity to nitrogen or ammonia in the electrocatalytic process, attracting extensive research interest. In this review, we discussed the background of denitrification requirements and the development status of bimetallic denitrification catalyst. Metallic cathode catalysts, such as noble-metal, 3d transition metal, main group metal, are described emphatically. Finally, present challenges and future outlook on bimetallic denitrification catalysts are depicted.