Cost-effective electrodeposited Ni-Co-TiO2 electrodes for boosting hydrogen evolution reaction in acidic and neutral electrolytes

Abstract

Despite the importance of energy for our life, the rapid consumption of fossil fuels with human population growth worldwide is imperative to find other sustainable sources of energy. A promising strategy is to assess earth-abundant and inexpensive materials as electrocatalysts for efficient green hydrogen production. Herein, nanocrystalline Ni-Co-TiO2 electrodeposited films on copper that have different Co atomic ratios are exploited as target cathodes for hydrogen creation from acid and neutral electrolytes. Different characterization techniques were utilized to identify the chemical composition, morphological structure, crystal lattice system, and unit cell parameters of the obtained bimetals-metal oxide nanocomposites. Ultrasonication with mechanically stirred plating baths was used to ensure the homogenous inclusion of TiO2 nanoparticles inside the bimetallic texture. The electrocatalytic activity of hydrogen evolution reaction (HER) over the designed nanocrystalline cathodes was investigated using voltammetric polarization, chronoamperometry, and electrochemical impedance spectroscopy techniques. The results showed that Ni-Co-TiO2 nanocomposites with somewhat low Co contents (8–9 at.%) displayed superior electrocatalytic HER activity in acid and neutral phosphate buffer (PB) electrolytes, outperforming by many times the other benchmark electrocatalysts. In 0.5 M H2SO4 solution, the Ni-8.2Co-4.8TiO2 cathode demonstrated the highest catalytic activity for the HER, minimal overpotential of 223 mV to deliver a current density of 10 mA cm−2, and small Tafel slope of 74.3 mV dec-1. While the Ni-9.2Co-4TiO2 electrocatalyst required a slightly higher Tafel slope of 79.5 mV dec-1 and an overpotential of 279 mV to convey the same current density of 10 mA cm−2 in 1 M PB electrolyte. The impedance data further confirm these results as these two cathodes showed the lowest resistance for the charge transport process on their surfaces among the other tested ones. The study confirmed that abundant transition bimetals/metal oxide nanocomposites are among the most promising long time stability electrodes for large-scale economic hydrogen fuel production technologies.