Highly efficient electrocatalysts composed of earth‐abundant elements are desired for water‐splitting to produce clean and renewable chemical fuel. Herein, a heteroatomic‐doped multi‐phase Mo‐doped nickel phosphide/nickel sulfide (Mo‐NiPx/NiSy) nanowire electrocatalyst is designed by a successive phosphorization and sulfuration method for boosting overall water splitting (both oxygen and hydrogen evolution reactions (HER)) in alkaline solution. As expected, the Mo‐NiPx/NiSy electrode possesses low overpotentials both at low and high current densities in HER, while the Mo‐NiPx/NiSy heterostructure exhibits high active performance with ultra‐low overpotentials of 137, 182, and 250 mV at the current density of 10, 100, and 400 mA cm−2 in 1 m KOH solution, respectively, in oxygen evolution reaction. In particular, the as‐prepared Mo‐NiPx/NiSy electrodes exhibit remarkable full water splitting performance at both low and high current densities of 10, 100, and 400 mA cm−2 with 1.42, 1.70, and 2.36 V, respectively, which is comparable to commercial electrolysis.

As we know, in plasmonic-enhanced heterogeneous catalysis, the reaction rates could be remarkably accelerated by generating hot carriers in the constituent nanostructured metals. To further improve the reaction rate, well-defined heterostructures based on plasmonic gold nanoparticles on MXene Ti3C2T x nanosheets (Au NPs@Ti3C2T x ) were rationally designed and systematically investigated to improve the performance of the oxygen evolution reaction (OER). The results demonstrated that the catalysis performance of the Au NPs@Ti3C2T x system could be easily tuned by simply varying the concentration and size of Au NPs, and Au NPs@Ti3C2T x with an average Au NP diameter (∼10 nm) exhibited a 2.5-fold increase in the oxidation or reduction current compared with pure Ti3C2T x . The enhanced OER performance can be attributed to the synergistic effect of the plasmonic hot hole injection and Schottky junction carrier trapping. Owing to easy fabrication of Au NPs@Ti3C2T x , the tunable size and concentration of Au NPs loaded on MXene nanosheets, and the significantly enhanced OER, it is expected that this work can lay the foundation to the design of multidimensional MXene-based heterostructures for highly efficient OER performance.

Density functional theory was used to study the effects of different types of oxygen-containing functional groups on the adsorption of oxygen molecules and single active oxygen atoms on carbonaceous materials. During gasification or combustion reactions of carbonaceous materials, oxygen-containing functional groups such as hydroxyl(-OH), carbonyl(-CO), quinone(-O), and carboxyl(-COOH) are often present on the edge of graphite and can affect graphite’s chemical properties. When oxygen-containing functional groups appear on a graphite surface, the oxygen molecules are strongly adsorbed onto the surface to form a four-member ring structure. At the same time, the O-O bond is greatly weakened and easily broken. The adsorption energy value indicates that the adsorption of oxygen molecules changes from physisorption to chemisorption for oxygen-containing functional groups on the edge of a graphite surface. In addition, our results indicate that the adsorption energy depends on the type of oxygen-containing functional group. When a single active oxygen atom is adsorbed on the bridge site of graphite, it gives rise to a stable epoxy structure. Epoxy can cause deformation of the graphite lattice due to the transition of graphite from sp2 to sp3 after the addition of an oxygen atom. For quinone group on the edge of graphite, oxygen atoms react with carbon atoms to form the precursor of CO2. Similarly, the single active oxygen atoms of carbonyl groups can interact with edge carbon atoms to form the precursor of CO2. The results show that oxygen-containing functional groups on graphite surfaces enhance the activity of graphite, which promotes adsorption on the graphite surface.

No abstract

MXene‐based material has attracted wide attention due to its tunable band gap, high conductivity and impressive optical and plasmonic properties. Herein, a hetero‐nanostructured water splitting system was developed based on N‐doped Ti3C2 (N10TC) MXene and NiFe layered double hydroxide (LDH) nanosheets. The oxygen evolution reaction performance of the NiFe‐LDH significantly enhanced to approximately 8.8‐fold after incorporation of N10TC. Meanwhile, the Tafel slope was only 58.1 mV dec−1 with light irradiation, which is lower than pure NiFe‐LDH nanosheets (76.9 mV dec−1). All results manifested the vital role of the N10TC MXene induced plasmonic hot carriers via electrophoto‐excitation in enhancing the full water splitting performance of the as‐prepared system. This work is expected to provide a platform for designing various plasmonic MXenes‐based heterogeneous structures for highly efficient catalytic applications.