The identification of catalytically active and stable bifunctional electrocatalysts for the oxygen reduction and evolution reaction (ORR/OER) would revolutionize rechargeable metal-air batteries and regenerative fuel cell technologies. In this study, we use density functional theory (DFT) calculations to systemically investigate 2D transition metal based tetracyanoquinodimethane (TM–TCNQ, TM = Cr-Cu, Ru-Ag, Pt, Ir) monolayers with single TM atoms catalysts (SACs) distributed periodically with high density. We calculate a lower limiting overpotential of η_lim = 0.33 V for Fe-TCNQ yielding a higher expected activity than that of Pt metal (0.48 V) for the ORR under acidic conditions. The catalytic performance of Fe-TCNQ for OER is, however, surpassed by Ni-TCNQs (η_lim = 0.46 V), which is identified as the highest among the candidates. By applying grafting axial ligands and external strain, the adsorption strength of reaction intermediates on TM reactive sites can be further optimized and enhances the activities of Mn-, Fe- and Ni-TCNQs for the ORR or the OER. Here, Fe-TCNQ-Cl (η_lim = 0.27/0.55 V), followed by Fe-TCNQ-CO (η_lim = 0.67/0.43 V), are predicted as novel, high-performance bifunctional ORR/OER catalysts with comparable limiting overpotentials to those of the best commercially used electrocatalysts, Pt (ORR: η_lim = 0.48 V) and RuO₂ (OER: η_lim = 0.42 V). In addition, the recently synthesized Fe-TCNQ possess excellent conductivity with fast electron transfer during the catalytic reactions. These results show 2D TM-TCNQ monolayers are durable, low-cost, and efficient catalysts for the ORR and the OER in metal-air batteries and fuel cells.

用于氧还原和放出反应（ORR / OER）的催化活性和稳定的双功能电催化剂的鉴定将彻底改变可充电金属空气电池和可再生燃料电池技术。在这项研究中，我们使用密度泛函理论（DFT）计算系统地研究了具有单个TM原子催化剂（SAC）分布的二维过渡金属基四氰基喹二甲烷（TM-TCNQ，TM = Cr-Cu，Ru-Ag，Pt，Ir）单层周期性地以高密度进行。我们计算出 Fe-TCNQ的较低极限超电势_ηlim = 0.33 V，在酸性条件下产生比ORR的Pt金属（0.48 V）高的预期活性。的Fe-TCNQ用于OER的催化性能，但是，通过Ni-TCNQs（η超过_LIM = 0.46 V），这被确定为候选中的最高电压。通过应用接枝轴向配体和外部应变，可以进一步优化反应中间体在TM反应位点上的吸附强度，并增强Mn-，Fe-和Ni-TCNQs对ORR或OER的活性。在这里，Fe-TCNQ-Cl（_ηlim  = 0.27 / 0.55 V），然后是Fe-TCNQ-CO（_ηlim  = 0.67 / 0.43 V），被预测为具有相似限制的新型高性能双功能ORR / OER催化剂Pt（ORR：_ηlim  = 0.48 V）和RuO ₂（OER：_ηlim） = 0.42 V）。另外，最近合成的Fe-TCNQ具有优异的电导率，并且在催化反应期间具有快速的电子转移。这些结果表明，二维TM-TCNQ单层是耐用，低成本且高效的催化剂，用于金属-空气电池和燃料电池中的ORR和OER。