Tunable formaldehyde sensing properties of palladium cluster decorated graphene.

The ability to tune the adsorption strength of the targeted gas on sensing materials is crucial for sensing applications. By employing first-principles calculations the adsorption and sensing properties of HCHO on small Pd n (n = 1-6) cluster decorated graphene have been systematically investigated. The adsorption energy is found to depend on the size of the Pd n cluster and can be tuned in a wide range from -0.68 eV on Pd(111) to -1.98 eV on the Pd3/graphene system. We also find that the Pd n /graphene (n = 5 and 6) systems have an appropriate adsorption energy for HCHO gas sensing. The current-voltage curves are calculated by the non-equilibrium Green's function method for the two-probe nano-sensor devices along both the armchair and zigzag directions. The devices constructed with Pd n /graphene (n = 5 and 6), having the highest absolute response over 20% at small voltages, should be applicable for HCHO detection. This work provides a theoretical basis for exploring potential applications of metal cluster decorated graphene for gas sensing.