The adsorption and decomposition of formic acid on clean and oxygen-dosed Pd(110)

Abstract

Theinteraction offormicacid (HCOOH) with Pd(ll0) wasstudiedusing TPO and XPS. At low doses, at an adsorption temperature of 140 K, HCOOH decomposed to yield CO, COa, H2 and H20 during TPD. CO and Hz were evolved in desorption-limited peaks at 470 and 320 K, respectively. The CO and H z 0 desorptions were saturated at very low doses indicating only a small degreeof formate dehydration in such a transient experiment. The CO2 and Hz evolution continued to increase with dose and the CO2 evolved in a decompmition-limited peak a t 237 K a t low doses which broadened to lower temperature with increasing coverage. This dehydrogenation of HCOOH was of first order with an activation energy of 40 kJ mol-'. At doses above 0.5 L molecularly chemisorbed HCOOH was observed to desorb at 210 K and at still higher doses physisorbed multilayers were present and desorbed a t 180 K. XPS confvmed the presence of CO above 250 K and formate below this temperature. When oxygen was pre-dosed the formate was significantly stabilized and its coverage increased, the CO desorption was removed and Ha was produced a t higher temperatures a t the expense of the H2 peak at 320 K.

Reaction of Formic Acid on Zn-Modified Pd(111)

“…The TPD data in Fig. 2 [26]. Dehydrogenation of adsorbed formates to produce CO 2 and adsorbed H atoms occurs at *240 K as evidenced by the reaction limited CO 2 peak at this temperature.…”

Integration of Homogeneous and Heterogeneous Catalytic Processes for a Multi-step Conversion of Biomass: From Sucrose to Levulinic Acid, γ-Valerolactone, 1,4-Pentanediol, 2-Methyl-tetrahydrofuran, and Alkanes

“…Since formic acid can be decomposed to carbon dioxide and hydrogen on palladium, silver or copper [16], the latter can be used for the hydrogenation of levulinic acid to GVL. Alternatively, formic acid could be used in the transfer hydrogenation of levulinic acid to GVL as well.…”

Catalytic and electro-catalytic oxidation of formic acid on the pure and Cu-modified Pd(111)-surface

“…Therefore the use of surface analytical methods which are also applicable in the electrochemical environment (''in situ") means an important step towards ''real" conditions. Studies on formic acid adsorption at transition metal surfaces have been performed since the 1970 s. Adsorption and reaction processes of formic acid have been investigated in UHV on poly-and single crystalline palladium [12][13][14][15][16][17] as well as on diverse other metal surfaces [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Also the adsorption and decomposition of formic acid under electrochemical conditions at different metal surfaces in sulphuric or perchloric acid with formic acid concentrations below 1 mol l À1 have been described several times [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51], including, in particular, studies on the influence of foreign metal atoms deposited on polycrystalline palladium on the oxidation of formic acid [52][53][54]…”