No abstract

The utilization of nonprecious metal electrocatalysts for water-splitting may be the ultimate solution for sustainable and clean hydrogen energy. MXene, an emerging two-dimensional material, exhibits many unique properties such as possible metal-like conductivity, hydrophilic surface, and rich chemistry, rendering a group of promising catalysts and catalyst support materials. In this study, exfoliated Ti3C2 MXenes serve as a substrate to perpendicularly grow uniform mesoporous NiCoP nanosheets through an in situ interface-growth strategy and subsequent phosphorization. The obtained Ti3C2@mNiCoP materials with a stable hierarchical sandwich structure possess excellent conductivity, large surface area, and uniform mesopores with high pore volume. With these beneficial properties, the Ti3C2@mNiCoP material exhibits superior overall water-splitting performance compared with that of its building-block counterparts, matching the state-of-the-art water-splitting electrocatalysts.

Non-platinum group metal (non-PGM) electrocatalysts for the oxygen reduction reaction (ORR) are generally composed of iron, nitrogen, and carbon synthesized through high-temperature pyrolysis. Among the various types of precursors, metal–organic frameworks (MOFs), zeolitic imidazolate framework (ZIF)-8 in particular, have often been used in the synthesis. The pyrolysis of ZIF-8 precursor relies on the use of Zn as a sacrificial metal (SM), and the optimal processing temperatures often exceed 1000 °C to generate active non-PGM catalysts. The high pyrolysis temperature tends to result in heterogeneous active moieties ranging from Fe single atoms to nanoparticles. In this study, we present the synthesis of non-PGM catalysts using Cd as the sacrificial metal instead of Zn. By using Cd, we were able to generate active non-PGM electrocatalysts from the MOF precursors at a low pyrolysis temperature of 750 °C, which helps preserve the single atomic iron active sites.

Due to the scarcity and high cost of precious metals, the hydrogen economy would ultimately rely on non-platinum-group-metal (non-PGM) catalysts. The non-PGM-catalyzed oxygen reduction reaction, which is the bottleneck for the application of hydrogen fuel cells, is challenging because of the limited activity and durability of non-PGM catalysts. A stabilized single-atom catalyst may be a possible solution to this issue. In this work, we employ a coordination-assisted polymerization assembly strategy to synthesize an atomic Fe and N co-doped ordered mesoporous carbon nanosphere (denoted as meso-Fe–N–C). The meso-Fe–N–C possesses a hierarchical structure with a high surface area of 494.7 m2 g–1 as well as a high dispersion of Fe (2.9 wt %) and abundant N (4.4 wt %). With these beneficial structural properties, the meso-Fe–N–C exhibits excellent activity and durability toward the oxygen reduction reaction, outperforming the state-of-the-art Pt/C electrocatalysts.

No abstract