We describe here an electro-reforming strategy to upcycle polyethylene terephthalate (PET) waste with simultaneous hydrogen production by a bifunctional nickel-cobalt nitride nanosheets electrocatalyst. PET plastics are digested in alkaline solution giving an electrochemically active monomer ethylene glycol (EG). The introduction of Co in Co-Ni₃N/carbon cloth (CC) promotes the redox behavior of Ni²⁺/Ni³⁺, which is beneficial for EG oxidation at an ultra-low potential (1.15 V vs. reversible hydrogen electrode (RHE)) and breaks through the limitation of high catalytic potentials of simple Ni-based electrocatalysts (1.30 V). In PET hydrolysate with Co-Ni₃N/CC couples, an integrated EG oxidation-hydrogen production system achieves a current density of 50 mA·cm⁻² at a cell voltage of 1.46 V, which is 370 mV lower than the conventional water splitting. The in-situ Raman and Fourier transform infrared (FTIR) spectroscopies and density functional theory (DFT) calculations identify the catalytic mechanism and point to advantages of heterostructure engineering in optimizing adsorption energies and promoting catalytic activities for EG oxidation.

Tin (Sn)-based materials have emerged as promising electrocatalysts for selective reduction of CO₂ to formate, but their overall performances are still limited by electrode structures which govern the accessibility to active sites, the electron transfer kinetics, and the catalytic stability. In this study, the heterostructured Sn/SnO₂ nanoparticles dispersed by N-doped carbon layer networks (Sn/SnO₂@NC) were synthesized by a melt-recrystallization method taking the low melting point of Sn (m.p. 232 ℃). The N-doped carbon layer networks derived from polydopamine could attract more electrons on the electrocatalyst, serve as conductive agents and protect the ultrafine nanoparticles from agglomeration and dissolution. The Sn/SnO₂@NC electrode exhibited the greatly enhanced performance for CO₂ reduction to formate in CO₂-saturated 0.5 mol·L^-1 aqueous NaHCO₃ solution, showing a selectivity of 83% at only -0.9 V vs. RHE with a sustained current density of 17 mA·cm^-2 for extended periods. By coupling the catalytic electrode with a commercially available RuO₂ catalyst as the anode, the long-term CO₂/H₂O splitting has been achieved. Furthermore, a rechargeable aqueous Zn-CO₂ battery with Sn/SnO₂@NC as the cathode and Zn foil as the anode was constructed. It could output electric energy with an open circuit voltage of 1.35 V and a peak power density of 0.9 mW·cm^-2.