Tuning a palladium(ii) phthalocyanine embedded hybrid electrocatalyst for the hydrogen evolution reaction

Abstract

Energy is an essential component of life, and its production and utilization must be compatible with the ecosystem. Hydrogen is considered a green and sustainable energy source among the various renewable and non-renewable energy sources. The hydrogen economy requires sustainable hydrogen production, which can be achieved through the electrochemical splitting of water using efficient and robust electrocatalysts. Platinum (Pt) and platinum-based catalysts are used because of their excellent catalytic activity, low overpotential, and energy consumption. However, palladium (Pd) has recently received significant attention as an electrocatalyst for energy production. Also, as per the volcano plot, Pd is a better replacement for Pt to achieve improved HER performance. Herein, palladium(II) tetranitrophthalocyanine (Pd(II)TNPc) is prepared and characterized by physicochemical and electrochemical tools. The catalytic activity of Pd(II)TNPc is evaluated for the HER, and the activity is noticed to significantly enhance embedding with Ketjen black (KB) carbon nanoparticles. The hybrid composite (Pd(II)TNPc + KB) showed activity comparable to that of the benchmark catalyst Pt/C for the HER. Linear sweep voltammogram (LSV) revealed a positive shift in the onset potential for the HER at GCE/PdT(II)NPc + KB compared to GCE/Pd(II)TNPc, suggesting that the HER is more feasible at Pd(II)TNPc + KB in 0.5 M H₂SO₄. The boost in HER activity of the composite catalyst in comparison to its original Pd(II)TNPc may be due to the embedded KB which improves the conductivity and number of active sites available for the adsorption of and offers larger active surface sites. The composite achieved a current density of 10 mA cm⁻² with a minimal overpotential of −187 mV, whereas Pt/C and Pd(II)TNPc exhibited an overpotential of −67 mV and −487 mV, respectively, at 10 mA cm⁻². Furthermore, the Pd(II)TNPc + KB composite demonstrated excellent stability for the HER. The fabricated hybrid composite with less than 8% of Pd in the total weight of Pd(II)TNPc can be employed as an excellent catalyst material for the HER. The lower amount of Pd in the catalyst assures an economical and efficient approach to exploit the HER efficiency employing the Pd(II)TNPc + KB hybrid composite.