Proton exchange membrane fuel cells convert hydrogen and oxygen into electricity without emissions. The high cost and low durability of Pt-based electrocatalysts for the oxygen reduction reaction hinder their wide application, and the development of non-precious metal electrocatalysts is limited by their low performance. Here we design a hybrid electrocatalyst that consists of atomically dispersed Pt and Fe single atoms and Pt–Fe alloy nanoparticles. Its Pt mass activity is 3.7 times higher than that of commercial Pt/C in a fuel cell. More importantly, the fuel cell with a low Pt loading in the cathode (0.015 mgPt cm−2) shows an excellent durability, with a 97% activity retention after 100,000 cycles and no noticeable current drop at 0.6 V for over 200 hours. These results highlight the importance of the synergistic effects among active sites in hybrid electrocatalysts and provide an alternative way to design more active and durable low-Pt electrocatalysts for electrochemical devices.

The poor durability of Pt-based nanoparticles dispersed on carbon black is the challenge for the application of long-life polymer electrolyte fuel cells. Recent work suggests that Fe- and N-codoped carbon (Fe–N–C) might be a better support than conventional high-surface-area carbon. In this work, we find that the electrochemical surface area retention of Pt/Fe–N–C is much better than that of commercial Pt/C during potential cycling in both acidic and basic media. In situ inductively coupled plasma mass spectrometry studies indicate that the Pt dissolution rate of Pt/Fe–N–C is 3 times smaller than that of Pt/C during cycling. Density functional theory calculations further illustrate that the Fe–N–C substrate can provide strong and stable support to the Pt nanoparticles and alleviate the oxide formation by adjusting the electronic structure. The strong metal–substrate interaction, together with a lower metal dissolution rate and highly stable support, may be the reason for the significantly enhanced stability of Pt/Fe–N–C. This finding highlights the importance of carbon support selection to achieve a more durable Pt-based electrocatalyst for fuel cells.

The sluggish kinetics of the oxygen evolution reaction (OER) is the bottleneck of water electrolysis for hydrogen generation. Developing cost-effective OER materials with a high value of practical application is a prerequisite to achieve extreme performance in both activity and stability. Herein, we report a "dual ligand synergistic modulation" strategy to accurately tune the structure of transition-metal materials at atomic level, which finally achieves satisfactory results for the unity between robust stability and high activity. Remarkably, the elaborately designed S and OH dual-ligand NiCo 2 (SOH) x catalyst exhibits an excellent OER activity with a very small overpotential of 0.29 V at a current density of 10 mA cm −2 and a strong durability even after 30 h accelerated aging at a large current density of 100 mA cm −2 , both of which are superior to most of the state-of-the-art OER catalysts so far. The density functional theory (DFT) calculations disclose that the synergy of OH and S ligands on the surface of NiCo 2 (SOH) x can delicately tune the electronic structure of metal active centers and their chemical environment, which results in optimal binding energies of the OER intermediates (*OH, *O, and *OOH) and a strengthened binding energy between metal and anion ligands, thus leading to an excellent intrinsically enhanced OER activity and stability, respectively. Meanwhile, the special nonmagnetism of NiCo 2 (SOH) x can significantly weaken the resistance of O 2 desorption on the catalyst surface, thus facilitating the O 2 evolution proceedings.

Slow kinetics of the hydrogen oxidation reaction (HOR) in alkaline electrolyte impedes the development of alkaline fuel cell systems. In this work, density functional theory calculations were used to study the HOR mechanism on several metals (Pt(110), Ir(110), Pd(110), Ni(110), and PtRu(110)), particularly by additionally considering the adsorption of hydroxyl species (OH*) on these metals. We found that the formation of OH* can transfer the potential-determining step of HOR mechanism from the H* oxidation to H 2 O* desorption under remarkably different effects of OH* on H* and H 2 O*. The comprehensive Δ r G−U relational diagrams for HOR/hydrogen evolution reaction show that, apart from the widely accepted activity descriptor, H* adsorption free energy (ΔG H* ), OH* adsorption free energy (ΔG OH* ), and H 2 O* adsorption free energy (ΔG H 2 O* ) also should be involved in predicting the HOR catalytic activity of metal catalysts in alkaline electrolyte. When the OH* formation free energy change (Δ r G OH* = ΔG OH* , at equilibrium potential) is more positive than the H* oxidation free energy change (Δ r G H*→H 2 O* = ΔG H 2 O* − ΔG H* , at equilibrium potential), ΔG H* as the sole descriptor indicates the HOR activity of catalysts due to scarce formation of OH* and a relatively weak H 2 O* adsorption at a relatively low overpotential, which happened in the case of Pt(110) and Pd(110). When Δ r G OH* and Δ r G H*→H 2 O* have little difference as in the case of Ir(110), both OH* formation and H* oxidation affect of the HOR and ΔG OH* and the enhanced ΔG H 2 O* by OH* should be involved in evaluating the HOR activity. In the case of Ni(110), a much lower value of Δ r G OH* than that of Δ r G H*→H 2 O* causes the surface to be mostly blocked by OH*, which suppresses the HOR. The combination of ΔG OH* , ΔG H* , and ΔG H 2 O* gives a more precise and comprehensive description of the HOR mechanism for metallic catalysts at different electrode potentials.

A 3D hierarchical Co/N-doped carbon nanotube/nanoparticle composite was successfully prepared as a high-performance ORR electrocatalyst, via pyrolysis of bimetallic Co, Zn-ZIF crystals coated on the surface of silica templates.