Controlled Surface Modification of Cobalt Phosphide with Sulfur Tunes Hydrogenation Catalysis

Abstract

Transition metal phosphides have shown promise as catalysts for water splitting and hydrotreating, especially when a small amount of sulfur is incorporated into the phosphides. However, the effect of sulfur on catalysis is not well understood. In part, this is because conventional preparation methods of sulfur-doped transition metal phosphides lead to sulfur both inside and at the surface of the material. Here, we present an alternative method of modifying cobalt phosphide (CoP) with sulfur using molecular S-transfer reagents, namely, phosphine sulfides (SPR3). SPR3 added sulfur to the surface of CoP and using a series of SPR3 reagents having different PS bond strengths enabled control over the amount and type of sulfur transferred. Our results show that there is a distribution of different sulfur sites possible on the CoP surface with S-binding strengths in the range of 69 to 84 kcal/mol. This provides fundamental information on how sulfur binds to an amorphous CoP surface and provides a basis to assess how number and type of sulfur on CoP influences catalysis. For the catalytic hydrogenation of cinnamaldehyde, intermediate amounts of sulfur with intermediate binding strengths at the surface of CoP were optimal. With some but not too much sulfur, CoP exhibited a higher hydrogenation productivity and a decreased formation of secondary reaction products. Our work provides important insight into the S-effect on the catalysis by transition metal phosphides and opens new avenues for catalyst design.

Co–Ti Bimetallic Complex-Induced Phase Modulation of Co@Black TiO2 for Catalytic Hydrogenation of Cinnamaldehyde

“…Moreover, the η4 adsorption mode significantly aids this reaction, leading to the production of a mixture of HCAL, COL, and HCOL from CAL hydrogenation. , Therefore, catalyst modification is crucial to enhance selective CO bond hydrogenation for achieving exclusive selectivity to specific target products. Although there are reports of selective hydrogenation of CAL to a particular product with a noble/non-noble metal catalyst, controlling reaction efficiency and selectivity to a particular hydrogenated product in the presence of monometallic catalysts is a challenging task. − Among few notable contributions in this regard the Yang and Liu group has made significant contributions to this field by developing a metal–organic framework (MOF) based monometallic catalyst (Co) as well as a bimetallic catalyst (Co–Mo, Co–W, and Co–Pt) and achieved high selectivity toward COL under optimal reaction conditions. , However, achieving maximum activity and selectivity with these non-noble metal-based catalysts still remains a challenge. Next, to assess the catalytic activity of the synthesized materials, we selected cinnamaldehyde (CAL) as a model substrate for hydrogenation.…”