Haichuan Zhang

Ultrahigh Hydrogen Evolution Performance of Under-Water “Superaerophobic” MoS2 Nanostructured Electrodes

The adhesion of as-formed gas bubbles on the electrode surface usually impedes mass-transfer kinetics and subsequently decreases electrolysis efficiency. Here it is demonstrated that nanostructured MoS₂ films on conductive substrates show a faster hydrogen evolution reaction (HER), current increase, and a more-stable working state than their flat counterpart by significantly alleviating the adhesion of as-formed gas bubbles on the electrode. This study clearly reveals the importance of a nano-porous structure for HER, which should be general and beneficial for constructing other gas-evolution electrodes.

Ternary NiCoP nanosheet arrays: An excellent bifunctional catalyst for alkaline overall water splitting

Exploring bifunctional catalysts for the hydrogen and oxygen evolution reactions (HER and OER) with high efficiency, low cost, and easy integration is extremely crucial for future renewable energy systems. Herein, ternary NiCoP nanosheet arrays (NSAs) were fabricated on 3D Ni foam by a facile hydrothermal method followed by phosphorization. These arrays serve as bifunctional alkaline catalysts, exhibiting excellent electrocatalytic performance and good working stability for both the HER and OER. The overpotentials of the NiCoP NSA electrode required to drive a current density of 50 mA/cm2 for the HER and OER are as low as 133 and 308 mV, respectively, which is ascribed to excellent intrinsic electrocatalytic activity, fast electron transport, and a unique superaerophobic structure. When NiCoP was integrated as both anodic and cathodic material, the electrolyzer required a potential as low as ~1.77 V to drive a current density of 50 mA/cm2 for overall water splitting, which is much smaller than a reported electrolyzer using the same kind of phosphide-based material and is even better than the combination of Pt/C and Ir/C, the best known noble metal-based electrodes. Combining satisfactory working stability and high activity, this NiCoP electrode paves the way for exploring overall water splitting catalysts.

Amorphous Co-doped MoS2 nanosheet coated metallic CoS2 nanocubes as an excellent electrocatalyst for hydrogen evolution

An amorphous Co-doped MoS2 coated highly crystalline pyrite-phase CoS2 hierarchical nanoarray exhibits ultrahigh activity towards acidic hydrogen evolution with a low onset potential (∼44 mV) and a small overpotential of ∼110.5 mV for driving the current density of ∼10 mA cm−2, ascribed to its novel hierarchical structure and the Co doping caused synergistic effects.

A metallic CoS2 nanopyramid array grown on 3D carbon fiber paper as an excellent electrocatalyst for hydrogen evolution

A CoS2 nanopyramid array with a low mass loading (∼0.625 mg cm−2) fabricated on 3D carbon fiber paper exhibits ultrahigh activity towards acidic hydrogen evolution with a low onset potential (∼61 mV) and a small overpotential (∼140 mV) for driving a current density of ∼100 mA cm−2, ascribed to the one-step solvothermal synthesis, unique 3D nanostructure and intrinsic metallic properties of the electrocatalyst.

Amorphous Co–Mo–S ultrathin films with low-temperature sulfurization as high-performance electrocatalysts for the hydrogen evolution reaction

Making defects, structuring and incorporating transition-metal elements have all been demonstrated as effective strategies to enhance intrinsic activity toward the hydrogen evolution reaction (HER), but how to integrate all these merits into one system is still a challenge. An amorphous Co–Mo–S ultrathin film fabricated via low-temperature sulfurization, with rich defects, hierarchical structuring and transition metal doping, shows excellent HER performance and good working stability in acidic media. Therefore, the low-temperature sulfurizing method and hierarchical nanoarrays are extremely important to construct highly active and stable electrocatalytic gas-evolution electrodes.

Superaerophobic RuO2 -Based Nanostructured Electrode for High-Performance Chlorine Evolution Reaction.

Constructing a nanostructured electrode with superaerophobic surface property (i.e., superlow adhesion to gas bubbles) has been strikingly highlighted as an advanced technology to minimize the energy loss during various electrochemical gas evolution reactions. Herein, aiming at enhancing the performance of chlorine evolution reaction (ClER), which holds the key for chlor-alkali industry as well as water treatment, a nanostructured RuO2 @TiO2 electrode is demonstrated to overcome the bubble shielding effect, thereby maximizing the working area and offering a robust working condition. Benefitting from the direct growing architecture and the superaerophobic surface property, this nanostructured RuO2 @TiO2 electrode exhibits an excellent ClER performance, reaching 50 mA cm-2 at a low potential of 1.10 V (vs SCE) with a Faradaic efficiency over ≈90%. Moreover, a prominent stability (250 mA cm-2 for 10 h) is observed for this nanostructured electrode, probably due to the small vibrations and scratching forces from gas product.

Probing the seeded protocol for high-concentration preparation of silver nanowires

Mass production of high-quality silver nanowires (Ag NWs) is of significant importance because of its potential applications in flexible transparent conductive devices. Halogen ions have been widely used for the synthesis of Ag NWs; however, owing to the lack of a deep insight into heterogeneous nucleation processes, usually a trace feeding amount (e.g. [Cl–] < 0.25 mM) is used, which in turn lowers the concentration of precursor ([Ag+]). Here we systematically investigated the nucleation and growth behavior of Ag NWs and concluded that the number of heterogeneous nucleation sites was determined by the total surface area of AgCl seeds, which indicated a linear relationship between the concentrations of Ag+ and Cl– during precipitation. Based on this mechanism, we successfully produced high-quality Ag NWs with Ag+ concentrations which were 20 times higher for a polyol system and 5 times higher for an aqueous system as compared to that in the previously reported strategies. Besides, by tailoring the heterogeneous nucleation sites by controlling the size of the AgCl seeds, the diameters of the final Ag NWs could be well controlled even at high Ag+ concentration. Based on the mechanistic understandings, this synthetic strategy could be extended to other AgX-seeds (X = Br–, I– and SO42–) and the basic principles can be applied to help rational synthesis of other high-yield metal NWs with tunable sizes.

Janus electrode with simultaneous management on gas and liquid transport for boosting oxygen reduction reaction

Oxygen reduction efficiency holds the key for renewable energy technologies including fuel cells and metal-air batteries, which involves coupling diffusion-reaction-conduction processes at the interface of catalyst/electrolyte, and thus rational electrode design facilitating mass transportation stands as a key issue for fast oxygen reduction reaction (ORR). Herein, we report a Janus electrode with asymmetric wettability prepared by partly modifying aerophobic nitrogen doped carbon nanotube arrays with polytetrafluoroethylene (PTFE) as a high performance catalytic electrode for ORR. The Janus electrode with opposite wettability on adjacent sides maintains stable gas reservoir in the aerophilic side while shortening O2 pathway to catalysts in the aerophobic side, resulting in superior ORR performance (22.5 mA/cm2 @ 0.5 V) than merely aerophilic or aerophilic electrodes. The Janus electrode endows catalytic performance even comparable to commercial Pt/C in the alkaline electrolyte, exploiting a previously unrecognized opportunity that guides electrode design for the gas-consumption electrocatalysis.