The development of electrocatalysts toward the hydrogen evolution reaction (HER) with high-current-density capability is critical for the practical application of water splitting for hydrogen production. While Pt-based materials are regarded as the most efficient HER catalysts, they suffer from scarcity and high price. Thus, it is of vital importance to lower the loading of Pt while maintaining high activity. Here, we report the fabrication of a monolithic aligned porous carbon film electrode co-modified with Pt single atoms and Pt nanoclusters (Pt SA/NC-AF) containing ultralow Pt content (0.038 wt.%) via a facile electrochemical deposition process. Benefiting from the aligned porous structure of the carbon film and the high exposure of the Pt species, the optimized Pt SA/NC-AF electrode exhibits outstanding HER performance in 0.5 M H₂SO₄ with exceptional intrinsic activity (turnover frequency (TOF) = 904.9 s⁻¹ at η = 100 mV) and ultrahigh mass activity (888.6 A·mg_Pt⁻¹ at η = 100 mV). Further, it can deliver an industrially relevant current density of 1,000 mA·cm⁻² at an overpotential as low as 139 mV. This work provides a feasible avenue for the rational design of metal single-atom and nanocluster catalysts and additionally promotes the application of ultralow-loading noble metal-based catalysts in high-rate hydrogen production.

Dispersing atomic metals on substrates provides an ideal method to maximize metal utilization efficiency, which is important for the production of cost-effective catalysts and the atomic-level control of the electronic structure. However, due to the high surface energy, individual single atoms tend to migrate and aggregate into nanoparticles during preparation and catalytic operation. In the past few years, various synthetic strategies based on ultrafast thermal activation toward the effective preparation of single-atom catalysts (SACs) have emerged, which could effectively solve the aggregation issue. Here, we highlight and summarize the latest developments in various ultrafast synthetic strategy with rapid energy input by heating shockwave and instant quenching for the synthesis of SACs, including Joule heating, microwave heating, solid-phase laser irradiation, flame-assisted method, arc-discharge method and so on, with special emphasis on how to achieve the uniform dispersion of single metal atoms at high metal loadings as well as the suitability for scalable production. Finally, we point out the advantages and disadvantages of the ultrafast heating strategies as well as the trends and challenges of future developments.

Herein, we develop a transient heating-quenching strategy triggered by Joule heating for the synthesis of single-atom cobalt- and nitrogen-doped graphene materials with three-dimensional porous monolithic architecture (denoted as CoNG-JH). The ultrafast Joule heating procedure simultaneously enables the reduction of graphene oxide and the incorporation of metal and nitrogen atoms into the graphene matrix within 2-second period. Meanwhile, the transient quenching avoids the extended heating-induced atom aggregation, ensuring the rapid and stable dispersion of atomic-scale CoN_x active sites in graphene. Additionally, the interconnected macropores and nanopores formed by the self-assembly of graphene sheets facilitate the unimpeded ion and gas transport during the catalytic process. When used as an electrode for the hydrogen evolution reaction (HER), the fabricated free-standing CoNG-JH exhibits high catalytic activity and durability with a low overpotential of 106 mV at 10 mA·cm⁻² and a small Tafel slope of 66 mV·dec⁻¹ in 0.5 M H₂SO₄ electrolyte. The presented synthesis and design strategy open up a rapid and facile route for the manufacturing of single atom catalysts.