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The surface oxygenated PdNiMnO-PF was used as a bifunctional catalyst for zinc–air batteries.

Single metal site Ni–N–C catalysts were designed concerning the particle size, metal content, and coordination structure for efficient CO2 reduction.

Changes in the local atomic arrangement in a crystal caused by lattice-mismatch-induced strain can efficiently regulate the performance of electrocatalysts for zinc–air batteries (ZABs) in many manners, mainly due to modulated electronic structure configurations that affect the adsorption energies for oxygen-intermediates formed during oxygen reduction and evolution reactions (ORR and OER). However, the application of strain engineering in electrocatalysis has been limited by the strain relaxation caused by structural instability such as dissolution and destruction, leading to insufficient durability towards the ORR/OER. Herein, we propose a doping strategy to modulate the phase transition and formation of self-supported cobalt fluoride–sulfide (CoFS) nanoporous films using a low amount of copper (Cu) as a dopant. This well-defined Cu–CoFS heterostructure overcomes the obstacle of structural instability. Our study of the proposed Cu–CoFS also helps establish the structure–property relationship of strained electrocatalysts by unraveling the role of local strain in regulating the electronic structure of the catalyst. As a proof-of-concept, the Cu–CoFS electrocatalyst with doping-modulated strain exhibited superior onset potentials of 0.91 V and 1.49 V for the ORR and OER, respectively, surpassing commercial Pt/C@RuO2 and benchmarking non-platinum group metal (non-PGM) catalysts. ZABs with the Cu–CoFS catalyst delivered excellent charge/discharge cycling performance with an extremely low voltage gap of 0.5 V at a current density of 10 mA cm−2 and successively 0.93 V at a high current density of 100 mA cm−2 and afforded an outstanding peak power density of 255 mW cm−2.

Recently, considerable attention has been paid to the stabilization of atomic platinum (Pt) catalysts on desirable supports in order to reduce Pt consumption, improve the catalyst stability, and thereafter enhance the catalyst performance in renewable energy devices such as fuel cells and zinc-air batteries (ZABs). Herein, we rationally designed a novel strategy to stabilize atomic Pt catalysts in alloyed platinum cobalt (PtCo) nanosheets with trapped interstitial fluorine (SA-PtCoF) for ZABs. The trapped interstitial F atoms in the PtCoF matrix induce lattice distortion resulting in weakening of the Pt–Co bond, which is the driving force to form atomic Pt. As a result, the onset potentials of SA-PtCoF are 0.95 V and 1.50 V for the oxygen reduction and evolution reactions (ORR and OER), respectively, superior to commercial Pt/C@RuO2. When used in ZABs, the designed SA-PtCoF can afford a peak power density of 125 mW cm−2 with a specific capacity of 808 mA h gZn−1 and excellent cyclability over 240 h, surpassing the state-of-the-art catalysts.

Proton-exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are promising power sources from portable electronic devices to vehicles. The high-cost issue of these low-temperature fuel cells can be primarily addressed by using platinum-group metal (PGM)-free oxygen reduction reaction (ORR) catalysts, in particular atomically dispersed metal–nitrogen–carbon (M–N–C, M = Fe, Co, Mn). Furthermore, a significant advantage of M–N–C catalysts is their superior methanol tolerance over Pt, which can mitigate the methanol cross-over effect and offer great potential of using a higher concentration of methanol in DMFCs. Here, we investigated the ORR catalytic properties of M–N–C catalysts in methanol-containing acidic electrolytes via experiments and density functional theory (DFT) calculations. FeN4 sites demonstrated the highest methanol tolerance ability when compared to metal-free pyridinic N, CoN4, and MnN4 active sites. The methanol adsorption on MN4 sites is even strengthened when electrode potentials are applied during the ORR. The negative influence of methanol adsorption becomes significant for methanol concentrations higher than 2.0 M. However, the methanol adsorption does not affect the 4e− ORR pathway or chemically destroy the FeN4 sites. The understanding of the methanol-induced ORR activity loss guides the design of promising M–N–C cathode catalyst in DMFCs. Accordingly, we developed a dual-metal site Fe/Co–N–C catalyst through a combined chemical-doping and adsorption strategy. Instead of generating a possible synergistic effect, the introduced Co atoms in the first doping step act as “scissors” for Zn removal in metal–organic frameworks (MOFs), which is crucial for modifying the porosity of the catalyst and providing more defects for stabilizing the active FeN4 sites generated in the second adsorption step. The Fe/Co–N–C catalyst significantly improved the ORR catalytic activity and delivered remarkably enhanced peak power densities (i.e., 502 and 135 mW cm−2) under H2–air and methanol–air conditions, respectively, representing the best performance for both types of fuel cells. Notably, the fundamental understanding of methanol tolerance, along with the encouraging DMFC performance, will open an avenue for the potential application of atomically dispersed M–N–C catalysts in other direct alcohol or ammonia fuel cells.

The alkaline hydrogen evolution reaction (A-HER) holds great promise for clean hydrogen fuel generation but its practical utilization is severely hindered by the sluggish kinetics for water dissociation in alkaline solutions. Traditional ways to improve the electrochemical kinetics for A-HER catalysts have been focusing on surface modification, which still can not meet the demanding requirements for practical water electrolysis because of catalyst surface deactivation. Herein, we report an interior modification strategy to significantly boost the A-HER performance. Specifically, a trace amount of Pt was doped in the interior Co2P (Pt–Co2P) to introduce a stronger dopant–host interaction than that of the surface-modified catalyst. Consequently, the local chemical state and electronic structure of the catalysts were adjusted to improve the electron mobility and reduce the energy barriers for hydrogen adsorption and H–H bond formation. As a proof-of-concept, the interior-modified Pt–Co2P shows a reduced onset potential at near-zero volts for the A-HER, low overpotentials of 2 mV and 58 mV to achieve 10 and 100 mA cm−2, and excellent durability for long-term utilization. The interior-modified Pt–Co2P delivers superior A-HER performance to Pt/C and other state-of-the-art electrocatalysts. This work will open a new avenue for A-HER catalyst design.

Carbon supports used in oxygen-reduction cathode catalysts for proton exchange membrane fuel cells (PEMFCs) are vulnerable to corrosion under harsh operating conditions, leading to poor performance durability. To address this issue, we have developed highly stable porous graphitic carbon (PGC) produced through pyrolysis of a 3D polymer hydrogel in combination with Mn. The resulting PGC features multilayer carbon sheets assembled in porous and flower-like morphologies. In situ high-temperature electron microscopy was employed to dynamically monitor the carbonization process up to 1100 °C, suggesting that the 3D polymer hydrogel provides high porosity at multiple scales, and that Mn catalyzes the graphitization process more effectively than other metals. Compared to conventional carbon supports such as Vulcan, Ketjenblack, and graphitized carbon, PGC provides an improved balance between high graphitization and hierarchical porosity, which is favorable for uniform Pt nanoparticle dispersion and enhanced corrosion resistance. As a result, Pt supported on PGC exhibits remarkably enhanced stability. In addition to thorough testing in aqueous electrolytes, we also conducted fuel cell testing using durability protocols recommended by the U.S. Department of Energy (DOE). After 5000 voltage cycles from 1.0 to 1.5 V, the Pt/PGC catalyst only lost 9 mV at a current density of 1.5 A cm−2, dramatically exceeding the DOE support durability target (