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Earth-abundant nickel is a typical non-noble-metal cocatalyst used for photocatalytic hydrogen evolution (PHE). Ni nanoparticles, however, tend to aggregate during the hydrogen production process, significantly lowering their PHE activity. To avoid aggregation, we used single atom form Ni and anchored them on vacancies in nitrogen-doped graphene (Ni-NG) as a cocatalyst for PHE. We demonstrated that Ni-NG is a robust and highly active cocatalyst for PHE from water. With only 0.0013 wt % of Ni loading, the PHE activity of composite Ni-NG/CdS photocatalyst improves by 3.4 times compared to that of NG/CdS, and it does not decay even after 10 rounds of 5-hour running. The quantum efficiency of Ni-NG/CdS for PHE reaches 48.2% at 420 nm, one of the highest efficiencies for non-noble-metal-based cocatalysts reported in the literature. Photoluminescence spectral analyses and electrochemical examinations indicated that Ni-NG coupled to CdS serves not only as an electron storage medium to suppress electron–hole recombination but also as an active catalyst for proton reduction reaction. Density functional theory calculations show that the high activity of Ni-NG/CdS composite results from the single Ni atoms trapped in NG vacancies, which significantly reduces the activation energy barrier of the hydrogen evolution reaction. This research may be valuable for developing robust and highly active noble metal free cocatalysts for solar hydrogen production.

Tuning and optimization of electronic structures and related reaction energetics are critical toward the rational design of efficient electrocatalysts. Herein, experimental and theoretical calculation demonstrate the originally inert N site within polyaniline (PANI) can be activated for hydrogen evolution by proper d-π interfacial electronic coupling with metal oxide. As a result, the assynthesized WO 3 assemblies@PANI via a facile redox-induced assembly and in situ polymerization, exhibits the electrocatalytic production of hydrogen better than other control samples including W 18 O 49 @PANI and most of the reported nobel-metal-free electrocatalysts, with low overpotential of 74 mV at 10 mA·cm −2 and small Tafel slope of 46 mV·dec −1 in 0.5M H 2 SO 4 (comparable to commercial Pt/C). The general efficacy of this methodology is also validated by extension to other metal oxides such as MoO 3 with similar improvements.

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Nanorod-like TiO 2 photocatalysts with controllable particle size for hydrogen production were synthesized based on H 2 Ti 3 O 7 precursors using hydrothermal and ion exchange methods. The characteristics of TiO 2 photocatalysts, such as morphology, specific areas and crystalline quality, can be adjusted by changing hydrothermal conditions, thus optimizing its photocatalytic activity for hydrogen evolution. The TiO 2 nanorod possesses the highest photocatalytic activity, even higher than P25, when the hydrothermal temperature is 140 o C, which should be ascribed to its large specific area and good crystalline quality. Non-noble metal Cu as a substitute of Pt was loaded on the surface of TiO 2 nanorod to promote the photocatalytic hydrogen production. It was confirmed that, during the photocatalytic reaction process, Cu 0 rather than CuOx acted as active sites to enhance the photocatalytic activity. The highest photocatalytic H 2 evolution rate of Cu/TiO 2 reaches 1023.8 μmol•h-1 when the amount of loading is 0.1 wt%, reaching the 20 times of that of bare TiO 2 (49.4 μmol•h-1) and approaching that of Pt/TiO 2 (1161.7 μmol•h-1). Non-noble metal Cu not only facilitated the separation of carriers, but reduced the overpotential of hydrogen evolution, thus promoting the photocatalytic activity for hydrogen production.

A novel route is developed to synthesize highly uniform N-doped porous carbon spheres (NCS) with a tailorable size ranging from 86 to 205 nm depending on their precursors of phenolic-resin-based analogues. Solid-state NMR and FTIR spectra confirm that the as-synthesized polymer spheres are composed of typical phenolic resin. After activation treatment with KOH, the NCS with a diameter of 86 nm possesses a high surface area of 1462 m2 g–1 coupled with hierarchical (micro and meso) pore structures. Upon these advantages, the prepared carbon sample endows the supercapacitor with high specific capacitance up to 247 F g–1 at 1 A g–1 with excellent rate performance and high cycling stability. Also, the specific energy density is 6.74 Wh kg–1 at a current density of 0.1 A g–1. Therefore, the as-prepared uniform N-doped porous carbon spheres represent a promising candidate for an efficient electrode material.