Room-Temperature Wet Chemical Synthesis of Au NPs/TiH₂/Nanocarved Ti Self-Supported Electrocatalysts for Highly Efficient H₂ Generation

Abstract

Self-supported electrocatalysts are a new class of materials exhibiting high catalytic performance for various electrochemical processes and can be directly equipped in energy conversion devices. We present here, for the first time, sparse Au NPs self-supported on etched Ti (nanocarved Ti substrate self-supported with TiH) as promising catalysts for the electrochemical generation of hydrogen (H) in KOH solutions. Cleaned, as-polished Ti substrates were etched in highly concentrated sulfuric acid solutions without and with 0.1 M NHF at room temperature for 15 min. These two etching processes yielded a thin layer of TiH (the corrosion product of the etching process) self-supported on nanocarved Ti substrates with different morphologies. While F-free etching process led to formation of parallel channels (average width: 200 nm), where each channel consists of an array of rounded cavities (average width: 150 nm), etching in the presence of F yielded Ti surface carved with nanogrooves (average width: 100 nm) in parallel orientation. Au NPs were then grown in situ (self-supported) on such etched surfaces via immersion in a standard gold solution at room temperature without using stabilizers or reducing agents, producing Au NPs/TiH/nanostructured Ti catalysts. These materials were characterized by scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), grazing incidence X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS). GIXRD confirmed the formation of AuTi phase, thus referring to strong chemical interaction between the supported Au NPs and the substrate surface (also evidenced from XPS) as well as a titanium hydride phase of chemical composition TiH. Electrochemical measurements in 0.1 M KOH solution revealed outstanding hydrogen evolution reaction (HER) electrocatalytic activity for our synthesized catalysts, with Au NPs/TiH/nanogrooved Ti catalyst being the best one among them. It exhibited fast kinetics for the HER with onset potentials as low as -22 mV vs. RHE, high exchange current density of 0.7 mA cm, and a Tafel slope of 113 mV dec. These HER electrochemical kinetic parameters are very close to those measured here for a commercial Pt/C catalyst (onset potential: -20 mV, Tafel slope: 110 mV dec, and exchange current density: 0.75 mA cm). The high catalytic activity of these materials was attributed to the catalytic impacts of both TiH phase and self-supported Au NPs (active sites for the catalytic reduction of water to H), in addition to their nanostructured features which provide a large-surface area for the HER.

Cathodic activation of synthesized highly defective monoclinic hydroxyl‐functionalizedZrO2nanoparticles for efficient electrochemical production of hydrogen in alkaline media

“…These results reveal that the improved HER catalytic activity not only survives as long as the potential (current) is held constant at −0.7 V vs RHE, but also is ameliorated during the operation, a highly promising aspect for the catalyst's practical use over long term operation. Catalyst activation during long‐term cathodic processes was a reproducible phenomenon in this work, and formerly obtained in our laboratory 73‐77 …”

“…Catalyst activation during longterm cathodic processes was a reproducible phenomenon in this work, and formerly obtained in our laboratory. [73][74][75][76][77] The evolved hydrogen is expected to incorporate into the crystal structure of ZrO 2 NPs creating new defect (catalytically active) sites for the HER. 78 Hydrogen incorporation into the material structure may also break ZrO 2 NPs down due to the hydrogen insertion-induced stress/strain.…”

Activating Titanium Metal with H2 Plasma for the Hydrogen Evolution Reaction

“…Surface modifications of Ti species have been conducted to improve the catalytic performance. Amin et al prepared TiH 2 layers on a Ti substrate by cathodic polarization and H 2 SO 4 etching, for both methods markedly increase the HER performance. , Liu et al found the generation of titanium hydrides on a Ti-2 alloy during galvanostatic polarization in acidic solution, and electrochemical experiments indicated that the titanium hydrides can catalyze the HER …”

Novel Ag/p-AgBr/n-BiVO4 Plasmonic Heterojunction Photocatalyst: Study on the Excellent Photocatalytic Performance and Photocatalytic Mechanism

“…Heavy metals and organic pollutants are often found in effluent; as a result, the removal of them is of great realistic significance with broad application prospects. Photocatalytic technology offers an opportunity to overcome the problem. − Titanium dioxide as a classical photocatalyst is widely used, but it has some shortcomings (low utilization of solar energy), which seriously limit its practical application. Therefore, designing a new and efficient photocatalyst to utilize visible light is the focus in the current study of photocatalysis. − Bismuth vanadate (BiVO 4 , n-type semiconductor) attracts increasingly bigger attention due to its excellent chemical stability, nontoxicity, and so on. , However, further improving photocatalytic performance is necessary due to its low ability to separate electron–hole pairs. − …”