NOVELTY - Deposition (M1) of platinum or palladium nano-particles or layers involves deposition of precursor complex solution on a substrate and chemical reduction of the precursor complex, where gaseous form of a reducing agent is used for the chemical reduction of the precursor complex.    USE - For deposition of platinum or palladium nano-particles or layers useful for preparing counter electrode for Gratzel cells; for preparing platinum or palladium electro-catalyst; for preparing immobilized platinum or palladium catalyst; for making electrically conductive platinum or palladium layer (claimed); as catalyst in fuel cells and for electro-oxidation/reduction of organic compounds.    ADVANTAGE - The method can easily deposit catalytic platinum or palladium nano-particles or layers at low temperatures. Using gaseous reducing agents it is possible to deposit metallic platinum (Pt) or palladium (Pd) on any number of substrates. The method solves the problem of depositing catalytic platinum or palladium on flexible thermoplastic substrates, which are not stable at higher temperatures. The practical method to deposit electrically conductive platinum or palladium layers at low temperature exhibits excellent adhesion and low sheet resistance. The deposited Pt nano-particles exhibit excellent adhesion and cannot be removed by wiping or cleaning in an ultrasonic bath. Since the surface energy rapidly decreases after particle formation because of the rearrangement of atoms on the surface, adhesion can be improved by suppressing the ageing of the nano-particles before their attachment. This is achieved by forming the nano-particles directly on the surface of the substrate at the gas-solid interface.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a counter electrode for Gratzel cells prepared according to the method (M1);    (2) platinum or palladium electro-catalyst prepared according to the method (M1);    (3) immobilized platinum or palladium catalyst prepared according to the method (M1); and    (4) an electrically conductive platinum or palladium layer prepared according to the method (M1), where a thin transparent hydrophilic layer is deposited to the substrate prior to the deposition of the precursor complex solution.