Bifunctional electrocatalysts for Zn–air batteries: recent developments and future perspectives

Abstract

The latest developments of bifunctional oxygen electrocatalysts for Zn–air batteries (ZABs) are comprehensively summarized and evaluated, laying special emphasis on the challenges, outlooks and directions of future research for the ZAB industry.

Superior Fe x N electrocatalyst derived from 1,1′-diacetylferrocene for oxygen reduction reaction in alkaline and acidic media

“…There are many strategies for the preparation of transition metal electrocatalysts explored [14][15][16] since Jasinski [17] reported for the first time in 1964 that cobalt phthalocyanine exhibited oxygen reduction activity. In the realm of heterogeneous catalysis, nano-carbon materials (porous carbon, graphene, carbon nanotubes, carbon fibers) and non-metallic (N, P, S) doped nanocarbon materials are widely used as catalysts and catalyst carriers [18][19][20].…”

Metal–organic framework based bifunctional oxygen electrocatalysts for rechargeable zinc–air batteries: current progress and prospects

“…The theoretical working voltage of ZABs is 1.65 V. 18,35 However, during the charge and discharge process, there is a large overpotential between the ORR and OER, which will reduce the operating voltage of ZABs to a certain extent (generally less than 1.2 V) and result in low energy round-trip efficiency. [41][42][43] Therefore, the main function of bifunctional electrocatalysts is to reduce overpotentials of the ORR and OER, and to achieve an efficient and stable catalytic reaction process.…”

“…[54][55][56] In addition, the clear structure and adjustable chemical coordination of MOFs not only bring great convenience to reveal the related catalytic mechanism, but also provide unlimited possibilities for their application in catalysis including using various metal active sites and appropriate ligands to construct conductive MOFs. 11,12,35,57 In a recent study, 2,3,6,7,10,11-hexaaminotriphenylene reacts with Ni 2+ in NH 3 aqueous solution to form Ni 3 (HITP) 2 . Dual probe and van der Waals electrical measurements prove that Ni 3 (HITP) 2 has a good conductivity.…”

“…14,31,[85][86][87] In addition, the introduction of multi-metal active centers can overcome the limitation that single metal active sites cannot obtain excellent bifunctional (ORR and OER) activity at the same time. 35,[88][89][90][91] Furthermore, the synergy between different metals or their interaction with other heteroatoms can further increase the activity of the catalysts.…”

“…31,32 (iii) The catalysts derived from direct pyrolysis of MOFs or MOF composites with other highly conductive substrates can enhance the conductivity of the catalysts, thereby accelerating the electron transfer. 26,[33][34][35][36] (iv) Heterostructured catalysts can be readily prepared by using MOF composites, which can create abundant interfaces and active sites. 37,38 (v) By rationally designing the structures of MOFs such as the size, porosity, hierarchical structure and distribution of active sites, 39,40 it is possible to obtain electrocatalysts with high catalytic activity and strong stability in the harsh catalytic environment of ZABs (Table 1).…”