Movable-type printing method to fabricate ternary FeCoNi alloys confined in porous carbon towards oxygen electrocatalysts for rechargeable Zn-air batteries.

Transition metal-based carbon catalysts are a promising class of electrocatalysts to enhance the efficiency of energy conversion and storage devices. However, it remains a challenging task to develop multi-metal alloy catalysts. Herein, ternary FeCoNi alloy nanoparticles (NPs) confined in nitrogen-doped carbon (NC) catalysts were fabricated via a facile movable-type printing method, where a range of transition metals confined in NC catalysts was prepared using the same technique except for the adjustment of the metal precursors. Due to the unique electronic structure and significant active sites of the medium-entropy alloy, the FeCoNi-NC catalysts demonstrated highly efficient bifunctional electrocatalytic activities for the oxygen reduction (E1/2 = 0.838 V) and evolution (Eoverpotential = 330 mV, 10 mA cm-2) reactions, which were comparable to those of Pt/C and RuO2. Moreover, the FeCoNi-NC-based liquid rechargeable ZABs displayed a substantial power density of 231.2 mW cm-2, and the homemade flexible ZABs also exhibited outstanding activity and cycling durability. Thus, this movable-type printing method is suitable for constructing a variety of multi-metal-based catalysts for metal air batteries.

Confined Ni nanoparticles in N-doped carbon nanotubes for excellent pH-universal industrial-level electrocatalytic CO2 reduction and Zn-CO2 battery.

Electrocatalytic reduction of CO2 (ECR) offers a promising approach to curbed carbon emissions and complete carbon cycles. However, the inevitable creation of carbonates and limited CO2 utilization efficiency in neutral or alkaline electrolytes result in low energy efficiency, carbon losses and its widespread commercial utilization. The advancement of CO2 reduction under acidic conditions offers a promising approach for their commercial utilization, but the inhibition of hydrogen evolution reaction and the corrosion of catalysts are still challenging. Herein, Ni nanoparticles (NPs) wrapped in N-doped carbon nanotubes (NixNC-a) are successfully prepared by a facile mixed-heating and freeze-drying method. Ni100NC-a achieves a high Faraday efficiency (FE) of near 100 % for CO under pH-universal conditions, coupled with a promising current density of CO (>100 mA cm-2). Especially in acidic conditions, Ni100NC-a exhibits an exceptional ECR performance with the high FECO of 97.4 % at -1.44 V and the turnover frequency (TOF) of 11 k h-1 at -1.74 V with a current density of 288.24 mA cm-2. This excellent performance is attributed to the synergistic effect of Ni NPs and N-doped carbon shells, which protects Ni NPs from etching, promotes CO2 adsorption and regulates local pH. Moreover, Ni100NC-a could drive the reversible Zn-CO2 battery with a high power-density of 4.68 mW cm-2 and a superior stability (98 h). This study presents a promising candidate for efficient pH-universal CO2 electroreduction and Zn-CO2 battery.

Synthesis, structure anatomy, and catalytic properties of Ag14Cu2 nanoclusters co-protected by alkynyl and phosphine ligands.

We report the synthesis, structure anatomy, and catalytic properties of Ag14Cu2(CCArF)14(PPh3)4 (CCArF: 3,5-bis(trifluoromethyl)phenylacetylene) nanoclusters, denoted as Ag14Cu2. Ag14Cu2 has a robust electronic structure with two free valence electrons, and it has a distinctive absorbance feature. Single-crystal X-ray diffraction (SC-XRD) disclosed that Ag14Cu2 possesses an octahedral Ag6 metal kernel capped by two Ag4Cu1(CCArF)7(PPh3)2 metal-ligand units. Remarkably, it exhibits excellent bifunctional catalytic performance for 4-nitrophenol reduction and the electrochemical CO2 reduction reaction (eCO2RR). In 4-nitrophenol reduction, it adopts first-order reaction kinetics with a rate constant of 0.137 min-1, while in the eCO2RR, it shows a CO faradaic efficiency (FECO) of 83.71% and a high current density of 92.65 mA cm-2 at -1.6 V vs. RHE. Moreover, Ag14Cu2 showed robust long-term stability with no significant decay in current density and FECO over 10 h of continuous operation in the eCO2RR. This study not only enriches the potpourri of alkynyl-protected bimetallic AgCu nanoclusters, but also demonstrates the great potential of employing metal nanoclusters for bifunctional catalytic applications.