The hydrogen evolution reaction (HER) is one of the two important half reactions in current water-alkali and chlor-alkali electrolyzers. To make this reaction energy-efficient, development of highly active and durable catalytic materials in an alkaline environment is required. Herein we report the synthesis of carbon-coated cobalt–tungsten carbide nanoparticles that have proven to be efficient noble metal-free electrocatalysts for alkaline HER. The catalyst affords a current density of 10 mA cm⁻² at a low overpotential of 73 mV, which is close to that (33 mV) required by Pt/C to obtain the same current density. In addition, this catalyst operates stably at large current densities (>30 mA cm⁻¹) for as long as 18 h, and gives nearly 100% Faradaic yield during alkaline HER. The excellent catalytic performance (activity and stability) of this nanocomposite material is attributed to the cooperative effect between nanosized bimetallic carbide and the carbon protection layer outside the metal carbide. The results presented herein offer the exciting possibility of using carbon-armoured metal carbides for an efficient alkaline HER, although pristine metal carbides are not, generally, chemically stable enough under such strong alkaline conditions.

Crystal facet engineering is an important strategy for fine-tuning the physical and chemical properties in many fields, which will provide an effective route to fundamentally understand the relationship between the surface structure and the electron state. Many researchers have worked on the technological performance improvement of noble metal nanoparticles and simple metal oxides by tailoring their crystal facets. Perovskite structure oxides are the most prominent mixed-oxide materials in the field of heterogeneous catalysis due to the acceptable catalytic activity and thermal stability. However, the utilization of perovskite oxides is still limited in comparison with noble metal catalysts because the most stable surface is usually terminated with non-catalytically active crystal facets. High-index facet tailoring may be an effective route to improve the activity of perovskite structure catalysts. So far, only several perovskite oxides have been reported on the crystal facet tailoring with well-defined polyhedral shapes. Herein, we review the recent progress in the facet tailoring arts in perovskite structure oxides. This review begins with a general introduction to facet related physical and chemical behavior and the potential facet-dependent applications. Then, the general principles of crystal growth and facet tailoring will be discussed. The principle for possible grown facets of perovskite structure oxides will be proposed. Various shape growth and facet tailoring of perovskite structure oxides will be reviewed in four parts: (i) tungsten and molybdenum trioxide (A⁰B⁺⁶O₃); (ii) niobate and tantalite (A⁺¹B⁺⁵O₃); (iii) titanate and zirconate (A⁺²B⁺⁴O₃); (iv) ferrite, chromite and manganite (A⁺³B⁺³O₃), including mixed-valence state perovskite compounds. The facet tailoring mechanism in perovskite oxides will be discussed in the next section. Finally, an overview of the promising future of facet dependent applications will be given as a perspective outlook. Fundamental understanding of facet tailoring is expected to open up strategies for the development of highly efficient perovskite oxide materials.

A simple treatment of La_0.5Sr_0.5MnO₃ with diluted HNO₃ creates more B-sites (rich) on the terminated perovskite surface and improves its catalytic activity toward CO oxidation, and the perovskite catalyst possesses a higher ratio of Mn⁴⁺/Mn³⁺ and thus enhances the O₂ adsorption capability, favourable for CO oxidation and catalytic activity.